Lake Tarpon Sink
Lake Tarpon Sink is actually in Tarpon Springs. Knight's Sink is located in Lake Tarpon. The two sinks are connected by a underground channel and both freshwater and saltwater flow between the sinks. Knight's Sink was separated from Lake Tarpon between 1967 and 1968 when the Army Corps of Engineers built the Lake Tarpon Canal to control flooding in the region.
Both sinks have been explored. Here is a divelog from Mike Emanuel's Cave Diving Page: "Upon entering the sink we made our way to the debris mound at a depth of 50', visibility was excellent and there was an abundance of marine life. The mound sloped down in a northerly direction where a sparse layer of hydrogen sulfide began along with the permanent guideline at 60'. With visibility reduced to 5 or 10 ft we made our way down to a depth of 205' and broke into warmer, gin clear water. The floor leveled off and line split in three directions, we followed one into what seemed to be the main passage. At a depth of 217' the vis took a turn for the worse again until one of us was smart enough to rise up off the line a little. The floor looked like a witch's cauldron with swirling clouds of gas that obscured sight of the line as we hovered just above it in gin clear water again. The percolation caused by our exhaust gases hitting the the 6" long mud straws on the ceiling gave some clue as to how long it was since someone had been through here and I started to pay real close attention to the condition of the guideline. The passage doglegged to the right, then left, and opened up into a huge conduit that was wide enough to swing a tractor trailer around in. The passage started to angle upward, and we made it back up to a depth of 60' before calling the dive. These sinks are chronicled by cave diving legend Sheck Exley in his biography Caverns Measureless to Man. After checking out his maps I can see that we almost completed the traverse to the lakeside basin, but who knows if that entrance is still accessible."