The limit for recreational divers is 40 meters or about 120 feet. There is danger in that the nitrogen that dissolves in the blood will cause clouding of mentation. Everything is blue. Red color (light) has long been filtered out. That would mean – getting stupid – in a very bad place. They demonstrate this by asking you to write numbers and letters on a board while at this level. My numbers and penmanship was definitely not too good. I’ve been down here a few times. No ill effects. But I realized that swimming behind my buddy is not a good idea. If I get stupid he’s not watching me. So nowadays I swim along side. So far so good. I might add the water is not that much colder when you are deep.
But for tropical fish it is cold enough to make them lethargic. So we chanced upon this puffer and he reluctantly moved off as we approached. At 120 feet we calculate about 9 minutes of safe time to be at this depth. The fish have no timer. How do they know when to go up? I’ve been told it is quieter at this depth. I just see it as too blue and not too colorful for images unless you have a strobe. Good thing I have a strobe now. …it’s more fun.