Riptide ukuleles are fairly new on the scene. They are made by Boulder Creek Guitars (in China).
Their most obvious feature is the oddly placed soundholes - one in the top corner of the soundboard and one on the side. The one on the soundboard is presumably to make way for some fancy bracing on the inside (they boast about the suspended bracing system on their guitars but their ukes don't seem to feature this). The one on the side lets the player hear more clearly what the sound coming out of the ukulele actually is. What you hear when you're playing can be quite different from what the audience hears - to get a better idea, stand right in front of a wall and play.
musicguymic checks out the Boulder Creek Riptide tenor ukulele.