These two are two minutes apart in Williston and often visited on the same trip, but they serve different people. Devil’s Den is the one for snorkelers and casual divers — a collapsed limestone cave with a wooden staircase down to the water and a skylight of hanging vines overhead, snorkel-or-dive only (no plain swimming), open to anyone comfortable in the water. Blue Grotto is deeper and more serious: a 100-foot cavern with a permanent air bell 30 feet down, built for certification dives and repeat cavern training.
Pick Devil’s Den if: you want the famous skylight photo and a snorkel, not a dive. Pick Blue Grotto if: you’re diving — especially training or certifying. Plenty of visitors do both back to back since they’re two minutes apart.
They sit about 1 miles apart, which makes doing both in one trip realistic. Here is how they actually differ.
| Devil's Den | Blue Grotto Dive Resort | |
|---|---|---|
| Our score | 8.5 / 10 | 7.8 / 10 |
| Entry fee | $30 snorkel / $48 dive (verified) | $61 dive / $23 snorkel (verified) |
| Hours | Mon-Thu 9am-5pm, Fri-Sun 8am-5pm | Open daily 8am-4pm |
| Magnitude | Subterranean spring | Karst sink/cavern |
| Nearest town | Williston | Williston |
| Best for | The most otherworldly swim in Florida | Florida's clearest training cavern — divers only |
| Good for | Scuba Diving, Snorkeling | Scuba Diving, Snorkeling |
| When to go | The first booking slot of a weekday morning. Light beams through the ceiling opening are strongest in the middle of the day, but the water is emptiest at opening. | Weekday mornings for the clearest water and fewest classes in the cavern. |
| Current conditions | Open · reservations required, weekends selling out | Open · reservations required |
Our honest verdict
Choose Devil's Den for the more photogenic, cavern-in-the-earth experience with fossils and daylight beams — snorkeling is allowed here (not at Blue Grotto's diver-only policy on weekends), making it more accessible to non-divers. Choose Blue Grotto for the better dive training experience — permanent guidelines, underwater lighting, and the famous 30-foot air bell make it exceptionally safe for open-water certification and practice. Blue Grotto costs more for diving ($61 vs Devil's Den's $48) but Devil's Den charges more for snorkeling ($30 vs Blue Grotto's $23, and Blue Grotto restricts snorkelers to weekdays).
Fees verified against both operators' official pricing pages, 2026.
Devil's Den
Devil's Den is a prehistoric spring inside a collapsed limestone cave — you descend a wooden staircase into the earth and surface-swim beneath a skylight fringed with hanging vines while sun rays cut through the water. There is nothing else like it in Florida, and the…
Local tip: Book the first morning slot: fewest swimmers, best light rays, clearest water. Water is 72°F in a shaded cave — a thin wetsuit (rentable) makes the visit far more comfortable. Bring your own gear if you have it — snorkel, mask, fins — since renting adds real cost on top of admission; one family reported paying around $100 total for a family of four once rentals were factored in. If you have underwater flashlights, bring them; the light beaming down through the karst window is beautiful, but a flashlight adds a lot when you're looking at the fossils in the walls. Weekdays after Memorial Day are reported as noticeably calmer than weekends, worth targeting if your schedule allows it.
Full guide, fees & map →Blue Grotto Dive Resort
Two minutes from Devil's Den, Blue Grotto is the serious sibling: a 100-foot-deep cavern with famously clear water, a permanent air bell 30 feet down, and platforms that make it the state's favorite dive-training site. This one is for divers — swimmers should book Devil's Den…
Local tip: Book alongside Devil's Den for a two-site Williston dive day. Midweek mornings get the glassiest water. Virgil, the resident softshell turtle, is a genuine fixture — divers feed and interact with her regularly, and she's become enough of a personality that staff and repeat visitors know her by name. Bring a good dive light regardless of certification level; at 90 feet it gets genuinely dark even in clear water.
Full guide, fees & map →