This version of Swimbuds is much larger than the last. It seems like they've doubled in size, but sound quality and volume have doubled, too. There are also a number of different earbuds to choose from now. Everyone's ears are shaped differently, and if you have a tighter, more sealed fit, that really helps the sound. There are some interesting options among the bud styles, and some of the gel style ones are giving me a very comfortable, great sounding fit.
I have only tried these swimming laps. There is a handy extension cable for longer cable runs so I assume they will work just fine for both kayaking and surfing. I don't think they're meant for SCUBA diving, however–the regulator would be too loud.