There are two Montauk Jetties (East and West) that flank the Montauk harbor channel. They guard the entrance into Block Island Sound and Long Island Sound. You can easily access either of them at Gosman's Dock on West Lake Drive or at the end of East Lake Drive adjacent to Montauk County Park. I particularly like the jetty on East Lake Drive because it is better for exploration, has fewer people, and has better facilities at the beach Park. Both jetties are pretty much the same in the department of underwater topography. They are constructed of large boulders and both sit on a sandy bottom. Depth gradually increases to 25 feet around the seaward points and visibility on good days holds in around 30 feet. The most notable feature of these two jetties are the many hiding spots for crabs and lobsters. Be careful grabbing the big ones. The sandy area around the outward edges of the jetties offer plenty of hiding spots for flounders and some small flukes. This area is also good for finding shells, but mostly augers and cones. Last dive I had there I found someone's fishing pole. It must have fallen in or perhaps was pulled out of the fisherman's hands when a large blue took the bait. During late August, one can expect to see schools of snappers and baby blues. I also spotted a few striped bass, too bad I didn't have my spear gun handy. If you're in the area and are looking for a decent shallow dive with interesting topography, head on over to Montauk's jetties and enjoy. One word of caution, stay away from the area between the jetties (the channel entrance) as boat traffic tends to be high, and watch out for fisherman on both sides of the jetties as they may inadvertently hook you while casting and retrieving. Always displaying a dive flag to alert fisherman is a good way to avoid contact.