@hitsusatsu11: DB wasn't meant to be taken seriously for much of its run, hence the toonforcing.
Hell DBZ was not meant to be taking seriously either which explains the hate it gets...
@Dream: yes but it does supply a possibility that saiyans do need oxygen just less then humans. The saiyans were able to survive in plan to eradicate the saiyans better then the humans, it also backs up the instances where it has shown saiyans breathing in space. Also about water just cause they may need less air doesn't mean they can't choke. Goku could have choked on the water which is why some people thing it was the lack of oxygen that gave him problems instead of a clogged airway.