

Best for advanced divers, 21-27m, shore entry, moderate current.
Mary Bay is a unique freshwater site in Grand Teton National Park defined by intense geothermal activity. Divers encounter active underwater geysers and fumaroles that vent water reaching 174°C into the cold lake environment, which averages 4°C at depth. This interaction creates extreme temperature gradients and dangerous thermoclines. The topography includes sandy bottoms marked by white mineral stains and fields of bubbles. Due to the depth of 21 to 27 metres, moderate currents, and low visibility ranging from 3 to 9 metres, this site is reserved for advanced divers. Shore entry is required, and divers must remain vigilant regarding boat traffic, entanglement risks, and down currents.
44.54850, -110.30200
Use altitude tables and ensure you have extra gas for drift.
Shore entry via rocky beach.
Expected in this region. No sightings logged here yet.
Depth
21-27m
Visibility
3-9m
Skill Level
Advanced
Entry
Shore
Current
Moderate
Best Time
Jul, Aug, Sep
There is no recorded marine life at this site.
No, this site is intended for advanced divers due to the depth, extreme temperature gradients, and hazardous conditions.
The depth ranges from 21 to 27 metres, with an average depth of 24 metres.
Mary Bay is accessed via shore entry.
Yes, the site is rated 5/5 for snorkelling, where observers can view bubble fields and mineral deposits from the surface.
Diving at Mary Bay in Yellowstone Lake requires the following certifications: Open Water. Always dive within your training limits.
The best months to visit Mary Bay in Yellowstone Lake are July, August, and September. Conditions outside these months can still be good but are less predictable.
Expect moderate currents at Mary Bay in Yellowstone Lake. Good buoyancy control and some drift diving experience is helpful.
Visibility at Mary Bay in Yellowstone Lake typically ranges from 3 metres to 9 metres. Conditions vary with weather, tides, and seasons.