The underwater park on the south east side is a terrific snorkelling spot. Take a boat to get to the best coral (not far out, but inaccessible by shore). The beaches are nice here to (Neat the Princess Hotel). Snorkeling is my favorite activity here. It is one of the best paces in the Caribbean to snorkel, especially if you like mult-colored coral.
Walking to town is nice, as the waterfront is very colorful.
The Seaquarium and its beach is a nice way to spend the day. Curacao is a great port to just walk around and check out the little shops on the main streeet. Very clean island, a couple of very nice casinos on the main street. The submersible tour is also a fun thing to do.
It's been a few years since I've been to Curacao but this was my favorite Island and I've seen quite a few. (Always mean to get back, but have kids now and don't want to fly all the way to San Juan)We rented Mopeds and explored the Island ourselves. The Island is not very big so no worries about getting lost. There are some very nice beaches on the far side of the Island. Town is very nice also, very colorful. At the time we went it was a short walk from the ship to rent Mopeds.