Recommendations for S90 replacement for island vacation, underwater shots

I'm still relying on my trusty Canon S90 which has served me well. But, I know there are a lot of newer options out now that weren't around in this category when I bought it. HD video is a notable upgrade that wasn't in the S90.

I'm going on vacation this fall and want something compact I can carry around with me on the island, and be able to take underwater snorkeling shots / video. So, ideally a camera that has an available underwater housing and can take HD video would be great. The newer Canon S100 and S110 haven't gotten as good of reviews as the S90 and S95, so I'm leery, but maybe for my purposes they'd be fine. The Canon housings for these are pretty pricey, but aftermarket cheaper ones are available, although maybe not quite as good.

The other thought would be to get a GoPro Hero for this purpose, as they take decent stills now too, and have cheap and widely available underwater housings. And just upgrade my S90 to something newer/better for normal vacation shots. FYI, I don't own a DSLR nor do I want to buy/carry one.

Thoughts?