Loch Raven Cliffs is a quarry site in the United States offering depths ranging from 3 to 73 metres. Access is via shore, though the site is primarily suited for advanced divers due to challenging conditions including low visibility of 1 to 3 metres, entanglement risks, and down currents. The water temperature fluctuates between 4C and 28C, with significant thermal stratification occurring during summer months. Divers should be aware of boat traffic and the presence of a thermocline. Parking is available near the site. Snorkelling is not recommended here, as the site receives a rating of 1/5 for that activity.

Pot Rocks is a freshwater canyon site located within the Maryland-Virginia Quarries. The site is defined by geological formations where the river has carved deep pots or holes into the bedrock. These underwater rock formations create a distinct topography for snorkellers to explore. The site is suitable for advanced snorkellers due to the presence of moderate currents and cold water conditions. Depths at this location range between 1 and 5 metres. Access to the water is via the shore, and parking facilities are available nearby for visitors.

Atlantic Coral Reef is an artificial reef exhibit located in the Maryland-Virginia Quarries. This controlled saltwater environment maintains a depth of 4 metres and offers a unique opportunity for divers to explore a contained habitat. The site is suitable for beginners, with shore entry and mild conditions. Divers can expect to encounter a variety of temperate marine life and invertebrates typical of the region. The dive typically lasts 40 minutes, with group sizes limited to six participants. Facilities at the site include parking and air fills. Divers should be aware of potential hazards, including entanglement, overhead environments, and sharp coral structures.

Hobo Beach at York Road Access offers a freshwater snorkeling experience within the Maryland-Virginia Quarries region. The site features a grassy bank entry leading into a deep, slow-moving section of the river. Depths at this location range from 8 to 39 metres. Water temperatures remain consistently cold, between 45 and 50 degrees Fahrenheit, due to the release from the nearby Prettyboy Reservoir. The site is suitable for beginners, though the deep water and cold temperatures require appropriate thermal protection. Facilities at the access point include parking and toilets. Typical sessions last approximately 45 minutes, with mild currents present throughout the area.

Bunker Hill is a deep pool located within the Maryland-Virginia Quarries near Prettyboy Reservoir. This freshwater site features a slower river flow, which allows for observation of the riverbed. Snorkellers can expect mild currents, though the water remains cold year-round, typically ranging between 45-50°F due to reservoir releases. The site is suitable for beginners and offers shore access. While specific sightings are not confirmed, the habitat supports various temperate freshwater fish and invertebrates typical of the region. Facilities at the site include parking and toilets. Due to the consistently low water temperatures, appropriate thermal protection is necessary for all visitors.

Hemlock Gorge is a shallow snorkelling site located below the dam near Prettyboy Reservoir. The area consists of shallow riffles and small pools shaded by hemlock trees. With an average depth of one metre and a maximum depth of two metres, it is suitable for beginners. Entry is via the shore. Conditions vary, with visibility typically ranging between one and four metres and moderate currents present. Snorkellers should be aware of potential entanglement hazards in the water. A typical session lasts approximately 30 minutes.

Fort Carroll is an artificial reef located 1609 metres from shore in the Maryland-Virginia Quarries. The site sits at a depth of 15 metres, with an average depth of 9 metres. Divers should expect visibility around 5 metres and mild currents, though conditions can vary. Access is by boat only. The artificial substrate supports a variety of local reef fish and invertebrates. Due to the low visibility and potential for entanglement within the structure, careful buoyancy control is required. Divers must remain aware of active boat traffic overhead and are advised to deploy a surface marker buoy before ascending.

Guppy Gulch is a 15-acre freshwater reservoir and former slate quarry offering shore-entry diving and snorkelling. The site features various sunken objects, including trains and trucks, alongside floating docks and inflatable water parks. Depths range from 5 to 18 metres, with an average of 10 metres. Conditions include mild currents and visibility between 2 and 6 metres. Divers should be prepared for significant thermoclines and cold water at depth. The site is suitable for beginners and supports night diving, with typical dive durations of 45 minutes. The habitat supports temperate freshwater fish and invertebrates typical of the region.