For activities, I'd suggest island hopping (it would take you the whole day). Dont forget your sunscreen, glasses and cash (there is a photographer who would take snaps of you - really nice pics actually, then have it sent to your accomodation).
Paraw sailing is also good in the afternoon especially when you watch the sunset. It gives you Moana/Maui vibes hahaha.
You can never go wrong with parasailing.