As a PADI DiveMaster, with over 500 dives, I have only one word to answer your question......DON'T !!!!! Too many seemingly little things of a negative nature, can happen while diving that can kill you when they escalate or compound with other seemingly little things. You could be carrying a dozen knives and still not make it! I read your previous post and felt it was answered correctly by kaptainkosmic, so i didn't add to his advice. However, I feel compelled to add a few comments here: decompression can be a factor at 20 to 25 feet, depending on bottom time, body size, quality of compressed air, and comsumption rate. In addition, I can't count the number of divers I have supervised on dives where in pre-dive briefings, a hard floor "depth" was set for a dive, but was broken by a careless diver or two in the group, without even realizing it. I personally have had to evacuate a diver recently who on a hard floor dive of 100', was at 130' and still descending when I reached her, and forced her careful ascent. I know, you are probably thinking "he is way to cautious", and you are partially right. However, it doesn't take a "rocket scientist to understand that to error on the safe side has a much better outcome than the alternative.
Be safe, have fun, and good luck with your underwater hunting.....more importantly, stay alive so you can tell us all about your awesome finds!