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Showers soak more then pools
(hackertalks.com)
A "Showerthought" is a simple term used to describe the thoughts that pop into your head while you're doing everyday things like taking a shower, driving, or just daydreaming. The best ones are thoughts that many people can relate to and they find something funny or interesting in regular stuff.
OP mentions fully submerged so the hair should not matter.
But even then, it's very likely that your head left the water long before the rest of you.