According to forum posts, Captain Hooks in Marathon offers snorkeling tours to Sombrero Reef and Coffins Patch. Another snorkeling destination mentioned is Looe Key, accessible via charters from Bahia Honda State Park and Ramrod Key, though these are not directly in Marathon but nearby.

Some travelers mentioned that while shore snorkeling in Marathon is possible, the experience may not be as rewarding as heading out to the reefs. The marine life visible from the shore primarily includes small tropical fish and seagrass, with the more vibrant coral and diverse sea life being further offshore.

Travelers have called out that the best snorkeling conditions are when the wind is under 10 MPH for optimal visibility. They also noted that water temperatures can be a deciding factor, especially during cooler months, which might affect the snorkeling experience.

According to forum posts, there are bus services available from Marathon to Key West. The Lower Keys Shuttle offers a route for approximately $4 each way. The schedule can be found on the City of Key West's official website. Travelers have indicated that the city bus fare from Marathon to Key West is around $2, but the last bus from Key West departs at 8 PM, which may not be suitable for late evening returns.

Some travelers mentioned the use of Key Express Shuttle, a more personalized transport option, though it's noted to book early, especially around busy periods like New Year's Eve. Other users suggested the possibility of renting a car for more freedom in travel times and stops, allowing exploration of scenic routes at one's own pace.

For many users, the choice between bus services and private shuttles or car rental depends on their specific travel needs, such as the desire to stay late in Key West or the need for more direct and flexible travel options.