Yeaaahhhhh... let's see:
The world, I don't see what's special about it apart from the fact that you need a boat to shop for groceries... Other than that it's full of dull sims with dull lives just like every other post-LN world. But at least the game doesn't run like crap on it.
The resort system is... well I actually haven't tried it but I can't really imagine what can be so great about it that's worth $50.
The boats are a rip-off. Apart from one or two fishing boats, a giant jetski and a shitty ass boat that passes along for a "speed boat" you don't get anything worth adding to your vehicle collection. No cigarette boats, no yachts, nothing. They work, sort-of, although I doubt they have much use anywhere other than on Isla Paradiso, not to mention the "boat parking space" or whatever is a pain in the ass to place anywhere, even on Isla Paradiso.
The house boats are... stupid. Who the fuck wants to live on a boat? Jesus Christ Maxis! Think! THINK!!
I haven't tried underwater exploration yet cause I can't find out how to learn the damn Scuba Diving skill.
As for the usual objects, clothing, etc... I think even UL added more stuff.
Biggest damn jetski I've ever seen: