Unearth The Voyage
There is a spot tucked into the southern tip of Illinois where the trees grow thick, the air smells like pine and fresh water, and a flooded quarry sits waiting with water so clear you can see straight to the bottom. Most people drive right past it without ever knowing it exists.
The trail to reach it is short enough for a casual afternoon, but what you find at the end is anything but ordinary. Mermet Springs has become one of the Midwest’s most talked-about outdoor destinations, attracting both certified divers and curious first-timers who just want to cool off and see something they have never seen before.
This article walks you through everything you need to know before you go.
Where Exactly You Will Find This Place
The address is 6724 N US-45, Belknap, IL 62908, a small community in Johnson County near the very bottom of the state. Southern Illinois does not always get the credit it deserves for natural beauty, but this corner of the region delivers in a big way.
The drive in feels rural and peaceful. You follow US-45 south through stretches of farmland and forest until a sign for Mermet Springs appears on the right.
The property sits just off the highway, easy to find but far enough from city noise to feel like a genuine escape.
The town of Belknap itself has a population of fewer than 200 people, which tells you something about how quiet and unhurried the whole area feels. You are not heading to a crowded tourist trap.
You are heading somewhere that rewards the people who actually bother to look it up and make the drive.
The Story Behind the Spring
Before Mermet Springs became a diving destination, it was a limestone quarry. When quarry operations ended and water began filling the pit naturally over time, what remained was a deep, spring-fed body of water with remarkable clarity.
The current owners transformed the site into a fully operational dive facility, and the results speak for themselves. Owner Glen has been a constant presence on the property for years, working alongside his staff to maintain water quality and keep the experience top-notch for every visitor who shows up.
Spring-fed water tends to stay cleaner and clearer than water sourced from runoff or surface lakes, which is a big part of why visibility here can reach impressive depths. The natural geology of southern Illinois created the conditions, but the people running the facility have done the work to keep it that way.
That combination of natural history and human dedication is what gives the place its character. It is not just a pretty hole in the ground.
It is a carefully maintained destination with a real backstory worth knowing.
What the Water Actually Looks Like
The first thing that grabs you when you walk up to the water is the color. It has that blue-green tint you usually associate with tropical destinations, not a rural Illinois county road.
On a sunny day, the surface almost glows.
Visibility underwater is one of the standout features of this site. On good days, divers report being able to see clearly for significant distances, which makes the experience feel more like exploring a natural aquarium than poking around in murky lake water.
The water temperature is a different story. The spring-fed quarry runs cold, especially at depth.
Past about 50 feet, a dry suit becomes much more than a luxury. Closer to the surface, a standard wetsuit handles things reasonably well during the warmer months, but you should always come prepared for cooler conditions than you might expect.
The clarity is what keeps people coming back year after year. When you can actually see what you are swimming through, the whole experience shifts from something you endure to something you genuinely enjoy.
Underwater Attractions That Will Surprise You
One of the most entertaining parts of a visit here is discovering what has been deliberately sunk to the bottom for divers to explore. The list of underwater attractions reads like an inventory from a very unusual yard sale.
There are sunken vehicles, including cars and a small plane. There is a train car sitting on the bottom.
There are other objects placed at various depths to give divers of all certification levels something interesting to swim around and through. The variety keeps each visit feeling fresh, even for people who have been coming for years.
Fish have made themselves at home around these structures, and hand-feeding them is a popular activity during try-dive experiences. First-timers often describe the fish feeding moment as a personal highlight, since it turns an already cool activity into something that feels genuinely interactive.
The intentional placement of these objects shows that the facility thinks carefully about what makes a dive site worth returning to. There is always something new to notice, even at a spot you have visited multiple times before.
Getting Certified Right Here on Site
Many visitors do not arrive as certified divers. They arrive as curious beginners, and Mermet Springs has built a solid reputation for turning that curiosity into a real skill set.
The facility offers full scuba certification courses through recognized training programs, and the instructors here take that responsibility seriously.
High school groups have completed their Open Water certification at this site, with some students earning their dive credentials before they even had a driver’s license. That kind of milestone tends to stick with a person for life.
The instructors are consistently described as patient, knowledgeable, and thorough. They do not rush students through the material.
They take time to address individual concerns, offer specific feedback, and make sure every person in the water feels genuinely prepared before moving to the next step.
Flexible scheduling makes the certification process accessible even for people with busy lives. Whether you are a complete beginner or someone looking to move up to a higher certification level, the team here can build a training plan that fits your timeline and your goals.
The Try-Dive Option for First-Timers
Not everyone who shows up at Mermet Springs is ready to commit to a full certification course, and that is perfectly fine. The try-dive program exists specifically for people who want to experience what scuba feels like before making a bigger decision about it.
During a try-dive session, an instructor stays right beside you throughout the whole experience. You do not go deep, and you do not go alone.
The focus is on helping you feel comfortable breathing underwater and moving around in a way that feels natural rather than terrifying.
People who describe themselves as hesitant or anxious before their try-dive often come out the other side talking about how calm and supported they felt. The instructors read their students well and adjust their approach based on what each person needs in the moment.
Feeding the fish, seeing the sunken objects, and just floating in that clear blue water for the first time tends to convert skeptics into enthusiasts pretty quickly. The try-dive is essentially a 90-minute argument for why everyone should at least try this once in their life.
Night Dives and Deep Dives for Experienced Divers
For certified divers who have already done the basics, Mermet Springs offers something a little more adventurous. Night dives are available at the facility, and they transform a familiar site into something that feels completely new.
When the sun goes down and the lights go off, the quarry takes on a different personality. Dive lights cut through the dark water, and the underwater structures look entirely different in artificial illumination.
Fish behave differently at night too, which gives experienced divers a reason to explore the same site from a fresh angle.
Deep dives are also part of the experience here. The quarry has enough depth to satisfy certified divers looking to push their skills and log dives at more challenging levels.
The cold water at depth is part of the challenge, and for divers who have the right gear and training, it adds to the appeal rather than subtracting from it.
The facility supports these advanced experiences with knowledgeable dive guides who know the site thoroughly. Having a guide who genuinely understands the quarry’s layout makes a meaningful difference on any dive, but especially on one done in the dark.
The Facilities and What to Expect on Arrival
The physical setup at Mermet Springs is well-organized and clean. Multiple pavilions are available for reservation, giving groups a shaded space to gear up, eat lunch, and hang out between dives without fighting over picnic tables.
Equipment rental is available on site, which is a practical detail that matters more than it sounds. Not everyone owns their own scuba gear, and having reliable rental equipment means you do not need to make a major investment just to try the sport for the first time.
The front desk staff set the tone for the whole visit. They are consistently described as helpful, knowledgeable, and genuinely happy to answer questions from people who have never touched a regulator in their life.
That welcoming attitude makes a real difference, especially for nervous first-timers who are already second-guessing themselves before they even get to the water.
The property is kept tidy, and the overall atmosphere feels organized without being overly corporate. You get the sense that the people running this place actually care about the experience each visitor walks away with, which is not something you can manufacture with signage alone.
Camping on the Property
A day trip to Mermet Springs is great, but staying overnight opens up a completely different kind of experience. The property offers camping, and several visitors have turned their diving weekend into a proper outdoor retreat by setting up camp right on site.
RV spots are available, and the ground is level enough to make setup straightforward. There are no water hookups on the property, so self-sufficient rigs or tent campers who plan ahead will have the smoothest time.
That is worth knowing before you pack, rather than after you arrive.
Spending the night means you can do an evening dive, sleep under the southern Illinois sky, and be back at the water’s edge first thing in the morning without a long drive in between. For serious divers, that kind of access is genuinely hard to put a price on.
The surrounding area is quiet and forested, which makes the camping feel like a natural extension of the whole outdoor experience rather than just a practical way to save on a hotel. Waking up near the water with another dive ahead of you is a solid way to start any morning.
Tips for Planning Your Visit
A few practical details can make the difference between a great day and a frustrating one. First, check the Mermet Springs website at mermetsprings.com before you go, since hours, availability, and reservation requirements can vary by season and group size.
Bring a wetsuit rated for cooler water, even in summer. The surface temperature is manageable during warm months, but the spring-fed depth will catch you off guard if you are not dressed for it.
A 5mm wetsuit is a reasonable starting point, and a dry suit is the smart call for deep dives.
Groups should reserve pavilion space in advance. The facility is popular enough that walk-ins can find themselves without a shaded staging area, which gets old quickly when you are trying to organize gear for multiple people in direct sunlight.
You can reach the facility by phone at 618-527-3483 if you have questions that the website does not answer. The staff are genuinely helpful over the phone and can point you in the right direction for certification schedules, rental availability, and anything else you need to sort out before making the drive to Belknap.
