Had to look up the place. Looks like the temperature gets a bit over 100F (38C) in some places. Acidity isn't an issue for the diver, although it could be damaging to their gear. Search results suggest this picture was taken at ~160 feet, which is a reasonable dive for any technical diver

I've done a similar dive profile in Yellowstone looking at hydrothermal vents. It's a reasonable dive for any experienced and qualified diver. I'm guessing they didn't have a technical diver, with equipment, on hand. It was likely much easier to drop a camera and bait