I think people are exaggerating and over reacting.

I took an empty altoid tin, wrapped electrical tape once around the seam, and dunked it in a bucket of water for close to an hour, and as you can see there isn't much water intrusion at all. If I wrap it a few more times I'd venture to say there wouldn't be any.

So while taking an altoid tin with your diving wouldn't be the best idea, just splashing or raining will be perfectly fine.