Depending on what type of player you are OP, if you can, I would wait for a sale or put it in a bundle (like I did). The world, BB and CAS are lovely - you can basically build a matching home from IL content which is so great (!!!), but gameplay is very lacking, and not expansion-worthy.
If you love occults (like I do), then mermaids are pretty disappointing - they don't act that much different to a normal sim, and they don't have a lot of different interactions with the water.
If you love jobs/gameplay, then most of this is already in the base game. The swimming actions for oceans are the same as pools (no new skill, diving is a rabbit hole and you can't move the camera underwater even when snorkeling), lounge chairs are in the base game (and the towel interaction is similar, so you're not missing much there), and so is the improved fishing. You have 1 active career in IL (I love how it changes the world, but it only works in one beach/area), and the rest are rabbit holes. In terms of expansion packs: swings are already in seasons, and while you can't tan/burn, if you play an occult in IL, you can't do that either (as my poor vamp sim found out).
On the other hand, I know some simmers really enjoy this game, so if you decide to get it, I hope you have lots of fun :).