some people use water bowls with lids on them and holes cut into the lids (water hides are usually designed this way). THis is handy for preventing spills, but it also poses a problem when folks don't account for the fluid displacement caused by the snake's body when they crawl in there (which makes a half full bowl suddenly completely full), or the fact that snakes are likely to search the edges of the bowl for an escape point with their nose instead of the middle of the lid where the hole is cut. This has claimed the life of more than one snake that i've heard of - so everyone please be careful.

Someone (was it Kevin McCurley?) was talking about a snake (an expensive one, too) flipping his bowl over on top of himself and it forming a seal, drowning the little guy. Very sad business, but sounds like something of a freak accident. Just think, yanno, before you leave things in your snakes' enclosures, and everything should be fine.