>Those make sense though. They are simple singular nouns that take an 's' for puralization. But 'water'?
>
>And I almost forgot, 'man - men' 'woman - women', and with 'women' we even change the pronunciation of the 'o'. What rule does that fall under, I wonder.

But wasn't it written that these are regular?

Yes it was, here: http://ndragan.com/lange/twouse.html - check part 2 with Roman - Romen, abdoman - abdomen etc.