The Marquesas Keys: An Uninhabited Atoll
The Marquesas Keys are a ring-shaped group of small, uninhabited mangrove islands approximately 30 nautical miles west of Key West. They form the only atoll in the Atlantic Ocean and are part of the Key West National Wildlife Refuge, managed by the U.S. Fish and Wildlife Service.
Navigation
The passage from Key West to the Marquesas takes approximately 3 hours at 10 knots. The approach requires careful navigation — the atoll is surrounded by shallow flats and coral heads. Enter through the main channel on the southwest side, which carries 6 to 8 feet at mean low water. A local captain or experienced crew is essential for first-time visitors.
Anchorage
The interior lagoon of the atoll provides protected anchorage in 5 to 8 feet over sand and grass bottom. Holding is good in moderate conditions. In strong southerly or westerly winds, the anchorage can become uncomfortable — monitor weather carefully and be prepared to relocate.
Fishing
The Marquesas are legendary among fly fishermen for permit — the flats surrounding the atoll hold some of the largest concentrations of permit in the world. Bonefish and tarpon are also present in significant numbers. The deeper waters outside the atoll produce yellowtail snapper, mutton snapper, and grouper. Spearfishing is prohibited within the wildlife refuge.
Wildlife
The islands are a critical nesting site for frigate birds, brown noddies, and sooty terns. Sea turtles nest on the sandy beaches. The surrounding waters are home to nurse sharks, eagle rays, and occasional manatees. The ecosystem is fragile — visitors should maintain distance from nesting areas and avoid walking on vegetated portions of the islands.
Regulations
The Marquesas are part of the Key West National Wildlife Refuge. No camping, fires, or overnight stays on the islands are permitted. Vessels may anchor in the surrounding waters. Fishing is subject to Florida state regulations and federal wildlife refuge rules.
Dry Tortugas National Park: Fort Jefferson
The Dry Tortugas, located 70 nautical miles west of Key West, are a cluster of seven small islands dominated by Fort Jefferson — the largest masonry structure in the Americas. The national park encompasses 100 square miles, of which 99 percent is water. It is one of the most remote and least visited national parks in the system, receiving approximately 80,000 visitors annually (compared to 12 million at the Great Smoky Mountains).
Fort Jefferson
Construction began in 1846 and continued for 30 years, though the fort was never completed. The hexagonal structure contains over 16 million bricks and was designed to control navigation in the Gulf of Mexico. During the Civil War, it served as a military prison — its most famous inmate was Dr. Samuel Mudd, convicted of conspiracy in the assassination of Abraham Lincoln. The fort is remarkably well-preserved and can be explored freely.
Navigation
The passage from Key West to the Dry Tortugas takes approximately 5 to 7 hours at 10 knots, depending on sea conditions. From the Marquesas, it is an additional 40 nautical miles west. The route crosses open water with no shelter — depart only in settled weather with a favorable forecast for the duration of the visit. The Gulf Stream does not affect this passage directly, but wind-against-current conditions in the Florida Straits to the south can create uncomfortable seas.
Anchorage
The primary anchorage is in the harbor on the south side of Garden Key, directly in front of Fort Jefferson. Depths are 5 to 15 feet over sand. The anchorage is exposed to southerly winds but well-protected from the prevailing northeast trades. A mooring ball system is in place — first-come, first-served. Vessels over 100 feet typically anchor outside the harbor and use tenders.
Fees & Permits
National park entrance fee is $15 per person (as of 2025), valid for seven days. There is no additional anchoring fee. Overnight anchoring is permitted. Generators must be turned off between 10 PM and 6 AM.
Snorkeling & Diving: Pristine Coral Reefs
The Dry Tortugas contain some of the healthiest coral reefs remaining in the Florida Keys, largely due to their remoteness and the protection afforded by the national park and the surrounding Tortugas Ecological Reserve.
Garden Key Snorkeling
The moat wall of Fort Jefferson creates an artificial reef that supports an extraordinary density of marine life. Snorkeling directly from the beach on the south side of Garden Key, visitors encounter sergeant majors, parrotfish, barracuda, nurse sharks, sea turtles, and occasional eagle rays — all within 50 feet of shore. Visibility typically ranges from 40 to 80 feet.
Loggerhead Key
The largest island in the group, located one mile west of Garden Key. The waters around Loggerhead Key offer excellent snorkeling and diving, with coral formations, sea fans, and large schools of fish. The Loggerhead Key lighthouse (1858) is visible from Garden Key.
The Windjammer Wreck
The remains of a 19th-century sailing vessel lie in 20 feet of water between Loggerhead Key and Garden Key. The wreck is encrusted with coral and serves as an artificial reef, attracting large grouper, moray eels, and schooling fish.
Tortugas Ecological Reserve
Established in 2001, this 151-square-nautical-mile no-take zone surrounds the park to the south and west. No fishing, anchoring, or collecting of any kind is permitted within the reserve. The reserve has been credited with significant recovery of fish populations, particularly grouper and snapper, which spill over into adjacent fishing areas.
Dive Conditions
Water temperature ranges from 72°F in winter to 84°F in summer. Visibility averages 60 feet and can exceed 100 feet in calm conditions. Currents are generally mild but can be significant near channel openings. The nearest hyperbaric chamber is in Key West — plan dives conservatively.
Planning Your Expedition
A voyage to the Marquesas and Dry Tortugas requires more planning than a standard Keys charter. The remoteness of these islands means that self-sufficiency is essential.
Recommended Itinerary (5 days from Key West)
Day 1: Key West to Marquesas Keys (3 hours). Afternoon fishing and snorkeling on the flats. Day 2: Full day at the Marquesas. Fly fishing for permit, exploring the atoll by tender. Day 3: Marquesas to Dry Tortugas (4 hours). Afternoon exploring Fort Jefferson. Day 4: Full day at the Dry Tortugas. Snorkeling, diving, bird watching. Sunset from the fort ramparts. Day 5: Dry Tortugas to Key West (5-7 hours). Fishing en route.
Provisioning
There are no services, fuel, water, or supplies at either the Marquesas or the Dry Tortugas. The yacht must carry all provisions, fuel, and fresh water for the entire voyage. Ensure adequate fuel reserves for the return passage plus a 25 percent safety margin.
Weather
This passage is weather-dependent. Do not attempt the crossing in winds exceeding 20 knots or when seas exceed 4 feet. Monitor NOAA weather forecasts continuously. The ideal conditions are northeast winds of 10 to 15 knots, which provide a comfortable beam reach on the outbound passage and a following sea on the return.
Communications
Cell phone coverage is unreliable beyond 15 miles from Key West and nonexistent at the Dry Tortugas. Satellite communication (Starlink, Iridium, or similar) is essential for weather updates and emergency communication.
Season
November through May offers the best conditions — settled weather, moderate winds, and excellent visibility. June through October brings calmer seas but increased risk of tropical weather and afternoon thunderstorms. The park is open year-round.
History of Fort Jefferson & the Dry Tortugas
Fort Jefferson is the largest masonry structure in the Americas and one of the most remarkable military engineering achievements of the 19th century. Understanding its history enriches the experience of visiting this remote outpost.
Construction (1846-1875)
The fort was designed to control navigation in the Gulf of Mexico and protect the vital shipping lanes between the Atlantic and the Gulf. Construction began in 1846 using over 16 million bricks, many transported from Pensacola and northern brick yards. The hexagonal fort was designed to mount 450 heavy guns and garrison 1,500 troops. However, advances in rifled cannon technology during the Civil War rendered the fort's brick walls obsolete before construction was completed.
Civil War Prison
During the Civil War, Fort Jefferson served as a Union military prison. Its most famous prisoner was Dr. Samuel Mudd, the physician who set the broken leg of John Wilkes Booth after the assassination of President Abraham Lincoln. Mudd was convicted of conspiracy and sentenced to life imprisonment at Fort Jefferson. He was pardoned in 1869 after heroically treating yellow fever victims during an epidemic at the fort. His cell is preserved and open to visitors.
Yellow Fever & Abandonment
Yellow fever epidemics in 1867 and 1873 devastated the garrison. The disease, transmitted by mosquitoes breeding in the fort's moat and cisterns, killed soldiers and prisoners alike. The Army abandoned Fort Jefferson as a military post in 1874. It served briefly as a quarantine station before being designated a national monument in 1935 and a national park in 1992.
Architectural Details
The fort's walls are 8 feet thick and 45 feet high, with three tiers of gun emplacements. The moat, originally designed as a defensive feature, now serves as one of the best snorkeling sites in the park. The parade ground inside the fort is surprisingly spacious, and the officer's quarters, powder magazines, and hot shot furnaces are accessible to visitors. The fort is approximately 75 percent complete — construction was never finished.
Bird Key & Bush Key
Adjacent to Garden Key, these islands are critical nesting sites for sooty terns and brown noddies. Between March and September, over 80,000 sooty terns nest on Bush Key, creating one of the most spectacular bird colonies in North America. Bush Key is closed to visitors during nesting season, but the colony is visible from the fort's ramparts.
Vessel Requirements & Safety Considerations
The voyage to the Marquesas and Dry Tortugas is not a casual day trip. It requires a seaworthy vessel, experienced crew, and thorough preparation.
Minimum Vessel Requirements
A vessel of at least 40 feet with a range of 200+ nautical miles is recommended. The vessel should be equipped with radar, GPS chartplotter, VHF radio, and ideally satellite communication. A watermaker is highly desirable, as fresh water is unavailable at either destination. The vessel should carry sufficient fuel for the round trip plus a 25% safety margin — there are no fuel facilities between Key West and the Dry Tortugas.
Navigation Hazards
The waters between Key West and the Marquesas contain numerous shallow areas, coral heads, and unmarked hazards. The approach to the Marquesas atoll requires careful navigation through shallow channels. The passage from the Marquesas to the Dry Tortugas crosses open Gulf of Mexico waters with no shelter for 40 nautical miles. Currents in this area can be unpredictable, particularly when the Gulf Stream meanders northward.
Emergency Procedures
The nearest Coast Guard station is in Key West, approximately 3-5 hours away by rescue vessel. For medical emergencies, Coast Guard helicopter evacuation is the primary option. Ensure the vessel carries an EPIRB (Emergency Position Indicating Radio Beacon), a comprehensive first-aid kit, and that at least one crew member has advanced first-aid or medical training. Satellite phone or Starlink connectivity is essential for emergency communication.
Anchoring at the Dry Tortugas
The anchorage at Garden Key is in 5-15 feet over sand. Holding is generally good, but the anchorage is exposed to southerly winds. In the event of a weather change, vessels may need to relocate to the lee side of the island group. The mooring balls in the harbor are first-come, first-served and may not accommodate larger vessels. Superyachts typically anchor outside the harbor and use tenders.
Night Navigation
The passage from the Marquesas to the Dry Tortugas is often undertaken as a night passage to arrive at dawn. The Loggerhead Key lighthouse (flashing white, 20-second interval, visible 18 nautical miles) serves as the primary navigational aid. The Garden Key harbor light marks the anchorage entrance. Radar is essential for night approaches, as the low-lying islands are not visible until close range.
Recommended Crew
For vessels under 60 feet, a minimum crew of two experienced mariners is recommended. For larger vessels, professional crew with experience in these waters is essential. Local captains familiar with the Marquesas and Dry Tortugas can be hired through Key West charter companies — their knowledge of channels, anchorages, and fishing spots is invaluable.
Frequently Asked Questions
Can we visit the Dry Tortugas by seaplane instead of yacht? Yes, Key West Seaplane Adventures operates daily flights from Key West to Garden Key (40 minutes each way). However, the seaplane visit is limited to a few hours on Garden Key. A yacht charter allows multi-day exploration of both the Marquesas and Dry Tortugas, with the freedom to snorkel, dive, fish, and explore at your own pace.
Is camping allowed at the Dry Tortugas? Yes, Garden Key has a small campground with 8 sites (first-come, first-served for individual sites, one group site by reservation). However, all supplies including fresh water must be brought in. Most yacht charter guests prefer to sleep aboard their vessel.
What fishing is available at the Dry Tortugas? Fishing is permitted in designated areas of the national park (not within the Tortugas Ecological Reserve). Species include yellowtail snapper, mutton snapper, grouper, and pelagics in deeper waters. A Florida saltwater fishing license is required. Spearfishing is prohibited within the park.
How rough is the crossing? In ideal conditions (northeast winds 10-15 knots), the passage is comfortable with 2-3 foot seas. In winter cold fronts (northwest winds 20-30 knots), the crossing can be very rough and should be postponed. The open Gulf of Mexico between the Marquesas and Dry Tortugas is the most exposed section. Always check NOAA marine forecasts before departing.
Can we combine this with a Keys charter? Absolutely. A popular itinerary is Miami to Key West (5-7 days) followed by Key West to Marquesas to Dry Tortugas and return (5 days), for a total of 10-12 days. This provides the most comprehensive Florida Keys experience available.
What about cell phone service? There is no cell service at either the Marquesas or the Dry Tortugas. Plan accordingly — download offline maps, inform contacts of your itinerary, and carry satellite communication for emergencies and weather updates.