SurfEars 4 - Pool use only so far, would be happy to use when whitewater kayaking.
Comfort: Not bad - good customisation, I can just about forget I've got them in.
Sound: I hear fine in them, no issues over long use in and out of the water. I can also equalise my ears with them in (not gone more than 3m deep).
Seal: They let in just a bit, prevents any sort of sloshing around or discomfort though and that's all I wanted.
Price: Amazing design and I don't regret buying, but I still baulk at the cost slightly.