Mermet Springs is an inland freshwater quarry dive destination in Belknap, southern Illinois. This Dive Site profile gives visitors an at-a-glance introduction and links to Gypsea Bleu’s firsthand visit report and history guide.
Quick facts
| Item | Details |
|---|---|
| Location | Belknap, southern Illinois, United States |
| Address | 6724 N US Highway 45, Belknap, IL 62908 |
| Environment | Freshwater quarry |
| GPS coordinates | 37.28416, -88.85828 — approximate site location (PADI location reference) |
| Best for | Scuba training, recreational dives and navigation practice |
| Highlights | Boeing 727 from U.S. Marshals, school bus and submerged vehicles |
| Daily admission | Divers $25; non-divers $8. Confirm current fees before visiting. |
| Official website | Mermet Springs |
Conditions and dive planning
Conditions reported October 23, 2026. This historical snapshot is retained from the earlier planning notes; it is not a live conditions report.
| Depth | Water temperature | Visibility |
|---|---|---|
| Surface | 71°F | 25–30+ ft |
| 15 ft | 71°F | 25–30+ ft |
| 20 ft | 70°F | 25–30+ ft |
| 45 ft | 51°F | 10–15 ft |
| 85 ft | 50°F | 10–15 ft |
| Bottom | 42°F | 10–15 ft |
Temperature and visibility change with season, weather, depth and dive activity. Check Mermet Springs’ latest official conditions before each visit. The live page has since been updated; these October 23 readings are preserved for reference.
Visibility and temperature vary considerably by depth and date. On our September 2026 visit, visibility declined around 30 feet. The quarry has pronounced thermoclines; plan exposure protection for your intended depth rather than surface conditions. Confirm current conditions, access requirements and available services directly with the dive operator before travelling.
Our experience at Mermet Springs
We have returned to Mermet Springs several times, including for SSI Open Water checkout dives and a September 2026 weekend with our RV. The quarry combines structured training opportunities with unusual underwater points of interest.
Official website, address and contact
Official website: mermetsprings.com — Mermet Springs (check here for the most recent hours, conditions, releases and fees).
- Address: 6724 N US Highway 45, Belknap, IL 62908
- Telephone: (618) 527-DIVE
- Email: Glen@mermetsprings.com
- Operator information: Hours, current conditions and entry fees
Admission and seasonal hours
The official website lists daily entry at $25 for divers and $8 for non-divers (verified October 2026). Operating schedules change by season: summer runs June–October, fall in November, winter December–March and spring April–May. Summer Fridays and Saturdays extend into the evening; winter Sundays are closed. Tuesday access in summer is by appointment; Wednesday is normally closed. Advance arrangements may allow other hours. Always verify the current schedule and pricing before departure.
Training, accessibility and facilities
| Facility / service | Details |
|---|---|
| Training platforms | The operator lists platforms at 5, 15, 20, 65, 85 and 100 feet. Depth selection must suit training, certification and conditions. |
| Entry | Four entry docks, with a lift at the primary dock for divers requiring assisted access. |
| Gathering areas | 18 covered pavilions with electrical power, fans and lights. |
| Equipment and fills | Scuba rental equipment, cylinders, air fills, nitrox blending, and a repair/inspection station; arrange specialty equipment in advance. |
| Other facilities | Heated showers, restrooms and a snack shack. |
| Programs | SSI Try Scuba, Open Water, referral checkout dives, specialty courses, skills updates and guided dives. The site also provides information about eligible veteran training reimbursements. |
See the official diver services and facility details and training programs.
Underwater attractions and navigation
| Attraction | Approx. depth | Location / highlight |
|---|---|---|
| Boeing 727 | Varies; confirm on site | Aircraft featured in U.S. Marshals |
| School bus | Confirm on site | Submerged bus |
| Railroad coal car | 55 ft | Between primary dock and Boeing 727 |
| Submarine | 60 ft | Northwest corner of train box-car |
| Ford pickup | 60 ft | Near 65-ft platform |
| Cessna | 55 ft | Between pickup and train box-car |
| Cessna 152 | 40 ft | Near cabin cruiser |
| Ambulance | 45 ft | Near Boeing 727 |
| Firetruck | 50 ft | Near Boeing 727 and train box-car |
| International semi-truck | 30 ft | Near Boeing 727 |
| Cabin cruiser | 40 ft | Between petting zoo and semi-truck |
| Bruce the Shark | 8 ft | Between motorcycle and petting zoo |
| Petting zoo | 12 ft | Near swim beach |
| Motorcycle | 12 ft | On platform in front of bus |
Signs and guidelines connect several features. Choose routes appropriate to your certification, experience and conditions, and follow site rules for wreck access.
See the official underwater attractions directory for descriptions and placement.
Camping and overnight accommodations
| Facility / service | Details |
|---|---|
| RV camping | Listed at $25 per night for two people, plus $8 for each additional person; 30-amp electrical connections, no potable water or sewer hookup. |
| Tent camping | Listed at $8 per person per night, first-come, first-served, with fire rings. |
| Shared facilities | Heated shower houses and restrooms. |
| Nearby lodging | The operator lists hotels, vacation rentals and other local options. |
Prices above reflect the official website when reviewed in October 2026 and can change. For reservations and current availability, visit Mermet Springs accommodations. Bring adequate fresh water if staying in an RV.
Before arriving: releases, safety and conditions
- Required release: The operator states that both divers and non-divers must complete a digital site release before arrival.
- Site rules: Review posted dive rules and the operator’s emergency action plan.
- Conditions: Temperature and visibility can shift dramatically with depth and season; use the dated official conditions report, rather than assuming surface temperatures reflect conditions at depth.
- Guided diving: Available by arrangement and limited by the diver’s certification; advertised guided-tour fees exclude entry, rental and fills.
- Training and equipment: Contact the operator ahead of time about rental sizing, air/nitrox, certification needs and guided services.
Official planning links: releases, rules, facilities and guided dives and today’s published hours and conditions.
Check opening dates, dive fees, training requirements, water conditions and current campsite amenities with Mermet Springs. Do not rely on historical visibility, temperature or depth observations as forecasts.
