About This Dive Site
Mary Bay, a sheltered embayment in Yellowstone Lake's East Inlet, provides accessible shore scuba diving at 7,733 feet elevation amid geothermal influences. Depths to 100 feet plus reveal spires and vents; 40 to 50 degrees F water, 10 to 30 feet viz. Shore entry via rocky beach; best July to September. NPS mandates: permits, no trace left, avoid hot zones.
Safety Considerations
Intermediate to advanced; altitude tables essential, stops at 10 feet. Vents pose burns, currents silt viz. Bears onshore; group dives. Bacteria advisory: nose protection.
Essential Gear
Drysuit, altitude computer, SMBs for exit. Fins for rocks, lights.