Is it dangerous to dive in 8 feet of water?

Answer 1

Not if your diving from less than about 6 feet fro the waters surface (which would cover most residential/hotel Swimming Pools). Only very experienced divers should try to dive into any 'shallow water' situation.

Answer 2

Drowning can happen in like less than 4 inches of water. There are several reasons you might drown while Scuba diving, including panicking, blacking-out (due to a multitude of possible medical conditions), entanglement, diving in caves or wrecks, seizures or convulsions, etc. If caught up in heavy surf, the diver could have the regulator removed from their mouth or get knocked unconscious by rocks/reefs.

Unless the water temperature is more than something like 80+ degrees, you will eventually become hypothermic, as your body's temperature regulation system will not be able to keep up with the increased heat loss (25x air) that occurs while you're in water. This will eventually result in death.

Ascending without exhaling from as little as 3ft (1m) with your lungs fully inflated can cause serious barotrauma which could cause several very undesirable outcomes including, having your lungs explode like a balloon, air-embolism, collapsed lungs, and death.

There's many marine organisms that can injure you at any depth (sharks, jelly-fish, sea-snakes, etc). Again, death is possible due to the injuries you could sustain.

If there are contaminants in the compressed air you are breathing, such as carbon monoxide, they can become even more toxic when breathed while underwater due to the increased pressure. As a side note, even Oxygen becomes highly toxic for many people around 200ft deep.

Another way to die scuba diving is to get run-over by other boaters who do not know they are supposed to stay away from marked diving locations (typically marked with a red flag with a white diagonal stripe in the US).

While relatively unlikely, if you stayed at 20ft for a very long time (many many hours), or decended and ascended many many times continuously over an extend period, it could be possible to get decompression illness (the bends). If serous enough, this could also result in death. I heard a story about a dive instructor who got bent from instructing many groups of students in a pool for the whole day... He had to go to the decompression chamber on Catalina Island.

I probably haven't covered all of the possible scenarios, but these are the main ones. Not that you should be "scared" or anything, but it's important to inform yourself about what CAN hurt you to minimize the chances you'll do something stupid that WILL hurt you. Learn from others' mistakes so you don't have to personally.