Was there between Christmas and New Year's. Walk into the spring basin. Middle of spring approx 10-15'. Begin descent into spring opening. Tall enough to stand up in at the opening. Begins to narrow down. I would guess it descends at about a 45 degree angle. Outflow was decent last time, I almost got wedged up pretty good at about 60'. Be aware of it. At about a depth of 45' I think this becomes a cave dive as I could not see daylight. There is a line on the right side of cave. I didn't stray from it very far. Visability at this time was about 25-30' in this section. Gravel bottom. Little silt to worry about. Restriction at about 80' made it impossible to swim against and explore further.
Conclusion: Open water divers can dive it, but should know what to expect and be equipped. Little danger of silt out due bottom composition and flow. Remember that narrow spaces equal stiff current. Similar to Ginnie Springs big basin in Florida, but with reduced vis. No fisherman to worry about during the week. Weekends may attract a crowd and possibility of getting snagged.
Can park about 75' away from basin opening. Heated restrooms about 175 yards downstream from basin. I had 58 degree water temp throughout.
Hope this helps. When I did it in February of last year, had much better vis. Dependent upon rainfall.
Any other questions, let me know. Happy to help.