Located in Marrianna (NW FL), Merrits Mill Pond offers excellent cave diving and snorkeling ventures.
To get there:
take I-10 to US 90, head east on US 90 for about 1 mile in Marrianna, turn right on S-71 for 1 mile, then right on S-164 for 3.5 miles. Look for a sign titled "Blue Springs". There are 6 springs that can be explored. There is cave diving here with cave certification. It's less crowded on a weekday because of the locals. A good day of diving can be experienced here. Blue Springs Park is operated seasonally (closed in the winter) and a canoe or small boat is necessary to reach this spring. A small store at the south side of the pond ( Hwy 90) rents canoe's. From Hwy 90 it's about 4.5 miles to reach Blue Spring. You will be well rewarded once you reach the spring.
Blue Spring has a very large cavern (see pic left for entrance) with extremely clear water. The entrance to the cavern begins at about 12 feet and the entrance to the cave at about 40 feet. This is one of the largest caverns I've ever been in and is excellent to snorkel or scuba dive. To scuba dive you must check in w/ the local sheriff's office for certification. However when I was there, they let 3 guys scuba dive the cavern/cave.