Blue Hole Spring sits at the end of a half mile walk through floodplain forest at the north entrance of Ichetucknee Springs State Park, in Columbia County a few miles east of O'Brien. Florida State Parks calls it the largest spring in the park. Cave divers have called it the Jug for generations, after the shape of the shaft that drops out of the pool floor. The open water is an oval of maybe 300 feet at its longest, ringed by cypress, oak and marsh grass, with no beach and no gradual shallows.

The spring holds 72 degrees every day of the year and runs about 40 feet deep over the vent. The USGS gauge here, station 02322688, logged discharge between 74 and 80 cubic feet per second through late 2025, close to 50 million gallons a day, and you feel it in the water. The boil pushes up out of the shaft hard enough to move a swimmer sideways. The park states plainly that Blue Hole should be used by experienced swimmers only because of the depth and the current, and that there is no lifeguard on duty. Near the rim the bottom is limestone ledge and eelgrass; past the rim it is a vertical hole in the rock that goes from blue to black.

Swimming and snorkeling are allowed and always have been, every day of the year from 8 a.m. until 30 minutes before sundown, at either Blue Hole or the Head Spring. Those two pools are the only places in the park where you may swim. Swimming anywhere on the Ichetucknee River itself is prohibited, and tubers have to stay on their float. Blue Hole Spring and the Blue Hole Trail close an hour before the park closes, earlier than the rest of the north entrance. Entry is by a small wooden deck and steps set into the bank, so you get in and you are immediately in deep water.

Blue Hole is the one spring in the park where scuba is permitted. Divers who intend to enter the vent must be cavern or cave certified, must dive in pairs, and have to carry gear the half mile in, which is why the park suggests bringing a cart. Roughly 500 feet of passage below the shaft has been mapped. Dives must finish an hour before sunset.

Fees are $6 per vehicle carrying two to eight people, $4 for a single occupant vehicle, $4 per motorcycle, and $2 for anyone walking or biking in. Entry is first come, first served, and paying online in advance does not reserve a spot. On hot summer weekends and holidays the north entrance lot fills and the gate closes until somebody leaves. Facilities at the north entrance include a restroom building next to the playground and picnic area, outdoor showers at the bathhouse, baby changing stations, picnic tables and grills, an accessible picnic pad by the Head Spring, and a food truck whose hours move with the season. There is no campground in the park.

At the swim areas the park bans food, coolers, glass, tobacco and vapes, speakers, toys and fishing gear, and allows only armbands, pool noodles or life jackets for flotation. No tubes in the springs. Dogs are not permitted on the Blue Hole Trail or in any water in the park. Alligators and snakes live along these trails and waterways, which the park says outright. The half mile trail crosses a long pedestrian bridge over the cypress swamp and is flat sand and boardwalk the whole way.