OP, what's the issue with the paddling? I'm utterly gobsmacked at what you've written. Is it the lack of suncream on skin that is bared? that is more of a potential issue, surely?
Sorry, this IS going to cause offence so I'm putting on my 'repels shit thrown at high velocity' suit... but they're kids. Really small kids. Stripped to what is the equivalent of swim pants, as mentioned by a previous poster. If that is your issue, then i would say remember, there were plenty of responsible parents, and stop sexualising small children. I agree with bamboo - what was going to happen? If adults want to get an eyeful of kids stripped donw, they can walk into Mothercare and take a catalogue.
What exactly are nurseries and the like to do in such a situation? They CANNOT contact every parent and they chose to remove clothing that might get wet, soggy... so they dont' - and a precious parent complains because a particular item of clothing got muddy? (OK, perhaps not that SPECIFIC incident, but can you see my point?....)
To me, bare skin is more of an issue. But you know what - it will probably be alright, anyway. They're kids!!!! They got wet and probably had HUGE amounts of fun.
Jeez. Is it just me?
(Sticking head above parapet, come on COME ON I can take it? 
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