I will be going to the Galapagos islands for a mostly land based trip. On those trips you usually snorkel at least once a day - with penguins, marine iguanas and sea lions. Note that this is NOT the same thing as diving the Galapagos!
I have been once before (in the days of film) and used a standard dive housing. That worked, but when you're right at the top and there is a lot of wave action it is pretty heavy and can be awkward. Waves whack the camera into your face, etc.
I usually use Seacam housings (1DS Mark III, 5D Mark III and have 1Dx on order). My sons use Seacam and Nauticam.
So my default housings for snorkeling will be those, but it has occurred to me that for rougher water a surf housing like SPL http://splwaterhousings.com/ might actually be better. They are lighter, and generally meant to be used with one hand.
Does anybody have any experience with using these right near the surface for snorkeling?