Poe Springs, located in High Springs ,FL, is one of the smaller springs. It's located in a large park with volleyball courts and large fields. This particular spring has a green tint to the water. This is probably caused by the algae covered bottom(see video). Depths here are about 25 feet.
The basin drops abruptly to a small cave entrance (about 2'x3'). The cave can be penetrated about 13 ft in if you can hold your breath and you aren't more than 200 lbs. No scuba is allowed.
From High Springs, take US 27-41 North to S-340 (poe springs rd.) west for 2.5 miles until you see the sign.
Video of poe springs underwater