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 and old enough (6+) to enter. 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, and priced accordingly higher for divers.
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.
Quick answer
- Pick Devil’s Den if you want the photogenic skylight-cave experience with fossils and daylight beams, and snorkeling — not diving — is the plan.
- Pick Blue Grotto if you’re diving — permanent guidelines, underwater lighting, and the famous air bell make it an excellent, safe spot for certification and cavern practice.
Both in one trip? Yes — they’re about two minutes apart. Book Blue Grotto’s morning slot first (it closes at 4pm), then Devil’s Den in the afternoon.
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-4:30pm, Fri-Sun 8am-5pm (verified, devilsden.com) | 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 · fees re-verified against devilsden.com Sept 2026 (walk-through pass now $15, was previously listed as $7) | Open · no reservation needed for a standard day of diving or snorkeling (night dives and group pool instruction do require advance arrangements) As of March 2026, at least one visitor reported visibility dropping below 2 feet during a heavily class-booked peak period, with every underwater platform occupied by a training group — a reminder that clarity here, like most spring caverns, swings with how many groups are stirring silt on a given day rather than staying constant. Weekday mornings remain the more reliable bet for clear water. The resort is closed on Thanksgiving, Christmas Eve, Christmas Day, and Easter. |
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. Reviewers consistently flag the same two friction points: the staircase down into the cave is steep and can feel intimidating with gear in hand, so budget a few extra minutes and take it slow rather than rushing; and the strict no-flotation, mask-snorkel-fins-on-the-whole-time rules catch first-timers off guard who expected something closer to a casual swim spot. Multiple reviews mention the changing rooms and lockers as basic but functional, and recommend bringing your own lock since not everyone finds one available on busy days. Regulars say the underwater visibility is noticeably better in the morning before dozens of fins have stirred up sediment near the entry stairs, reinforcing the value of booking that first slot. People who've done both note the cave feels genuinely small and intimate compared to open springs — there's no wide area to spread out, so a full 90-minute slot with a crowded group can feel closer and busier than photos suggest.
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. Rental gear is first-come, first-served only — you can't reserve it ahead, so arrive early if you're counting on borrowing anything. Regulars specifically call out staff members Kurt, Harry, and Sandy by name for being especially helpful with first-time cavern divers. If you're bringing students to train in the on-site pool, budget $6/student with a 2-hour and 4-student minimum, plus the daily walk-in fee for any non-diving students in the group.
Full guide, fees & map →Where they actually differ
Fees and what’s included
Devil’s Den charges $30/person for a reserved 90-minute snorkel session (which includes a John’s Oasis day pass) and $48 for scuba diving, first-come-first-served with Open Water certification required. A $15/person day pass lets non-swimmers see the grounds (no water access). Blue Grotto flips the pricing: diving is the pricier ticket at $61/person daytime ($31 for a night dive), while snorkeling is cheaper at $23 — but only on weekdays or as part of a group that includes divers, plus a $7 non-diver walk-in rate. In short: Devil’s Den is cheaper to dive, Blue Grotto is cheaper to snorkel, if you can even get a snorkel slot there.
Crowds, reservations and capacity
Both require reservations and both sell out on weekends. Devil’s Den’s booking is genuinely strict — snorkel reservations are non-refundable (though one free date change is allowed with 72 hours’ notice), and people who show up without a booking have been turned away after driving hours. Blue Grotto’s crowding varies more by day — weekends and dive-class days can feel busy, but weekday visits are frequently described as nearly empty, sometimes just one other group on site. Both are booking through weekday mornings for the clearest, least-stirred-up water.
The water and what you can do in it
Devil’s Den is a sinkhole cave, not a true dive site in the technical sense — snorkelers are capped at 8 feet (deeper sections are for certified divers only), no free-diving, no flotation devices, mask/snorkel/fins on the whole 90 minutes. Sunlight beams down through the ceiling opening onto Pleistocene-era fossils in the walls, which is the whole draw; reviewers regularly compare it to Mexican cenotes. Under-6s aren’t allowed in the cave at all, no exceptions.
Blue Grotto is a genuine 100-foot cavern with a lit, guideline-equipped layout and the famous 30-foot air bell fed by a surface compressor, where divers can surface, pull a regulator, and talk underwater. Open Water certification covers the cavern zone (recommended 60ft max); the deeper cave beyond that requires full cave certification and a guide. This is a training and certification site first, a casual snorkel spot a distant second.
Camping/lodging and facilities
Both offer overnight stays, which is unusual for spring-adjacent sites this small. Devil’s Den has an RV park, four cabins, a remodeled double-wide, and a tent camping area, plus a swimming pool for non-snorkelers and The Ivy House restaurant on property. Blue Grotto leans more resort than rustic for families: a pool, basketball court, and ping pong table for non-diving kids, camping around $15/site, and cabins from tight efficiency units to two-bedroom options.
Getting there and parking
They’re genuinely two minutes apart in Williston — among the closest pairings on this whole site. Devil’s Den’s hours run Mon–Thu 9am–4:30pm, Fri–Sun 8am–5pm; Blue Grotto is open daily 8am–4pm. Note the different weekday closing times before planning a same-day double.
Who each is for
Devil’s Den is for snorkelers, photographers, and anyone who wants the singular skylight-cave experience without needing a dive certification. Blue Grotto is for certified divers, especially anyone training or certifying, thanks to the permanent air bell and guided cavern layout.
Doing both in one trip
At roughly a mile apart in the same town, Devil’s Den and Blue Grotto are about as easy a same-day pairing as exists in Florida. Divers commonly book both for a two-site Williston dive day — Blue Grotto’s cavern and air bell in one session, Devil’s Den’s cave and fossils in the other. Snorkelers without a dive cert should lean toward Devil’s Den, since Blue Grotto restricts snorkeling to weekdays or diver-accompanied groups. Given the differing hours (Devil’s Den opens later on weekdays, Blue Grotto closes earlier every day at 4pm), book Blue Grotto’s morning slot first if doing both in one day, then move to Devil’s Den for the afternoon.
Our pick
Pick Devil’s Den if you want the more photogenic, cavern-in-the-earth experience with fossils and daylight beams, and snorkeling (not diving) is the plan — it’s the more accessible of the two for non-divers.
Pick Blue Grotto if you’re diving and want the better training experience — permanent guidelines, underwater lighting, and the famous air bell make it exceptionally safe for open-water certification and cavern practice.
For a snorkeler with no certification, Devil’s Den is the only real option between the two. For a diver working toward certification, Blue Grotto is the stronger training site.
FAQs
Do you need to be a certified diver to visit either spring?
No, not for Devil’s Den snorkeling — reservations are required, but anyone 6 and older comfortable in the water can snorkel there. Blue Grotto’s water access is mainly for certified divers; snorkeling is available but restricted to weekdays or groups that include divers.
Can you do Devil’s Den and Blue Grotto in one day?
Yes — they’re about two minutes apart by car, and plenty of divers book both for a single Williston dive day. Just note Blue Grotto closes at 4pm daily while Devil’s Den stays open later on weekends (until 5pm), so plan the tighter-hours stop first.
Which is better for kids: Devil’s Den or Blue Grotto?
Devil’s Den, for kids 6 and up who are comfortable snorkeling in cold water — it’s a memorable, kid-friendly experience by most reviewer accounts, though under-6s aren’t allowed in the cave at all. Blue Grotto is oriented toward certified divers and isn’t really built around a casual family swim.