Illinois Beach at Pearl Lake features a unique rocky and sandy lakebed, representing the only remaining beach ridge shoreline in the state. This freshwater site is part of the Lake Michigan Dune Section, offering geological formations for snorkelers to explore. Conditions vary, with depths ranging from 2 to 6 metres and an average of 4 metres. The site is accessed from the shore and is suited for intermediate snorkelers due to moderate currents, potential surf, and variable visibility between 3 and 10 metres. Water temperatures fluctuate significantly throughout the year, ranging from 2C to 22C, with the warmest conditions typically occurring in August.

Three Oaks Recreation Area at Pearl Lake is a freshwater site featuring an artificial reef and dedicated training infrastructure. Divers access the water from the shore or a floating dock located east of the marina. The site offers three training platforms positioned 100 feet apart at a depth of 7.6 metres. The average depth across the area is 10 metres, with a maximum depth of 14 metres. Conditions include mild currents and visibility ranging from 3 to 12 metres. Divers should be prepared for a noticeable thermocline at approximately 7.6 metres, as well as potential hazards including boat traffic, cold water, entanglement risks, and fluctuating visibility.