Really need a little more info to help.... where are you staying, who are you booked with?

I am Staying in Port des Torrent, near san an, in the seaveiw hotelcan you take day trips to other Islands? Thank you!

Boat trips to Formenterra are realatively inexpensive, I know they go from Santa Eulalia and Ibiza Town, not sure if they go from San An though, might be the wrong side of the island.

To go to the other major islands by boat is a far more expensive affair and requires booking a ferry. I can point you in the right direction if you wanted to go that.

The caves are worth a visit, you will probably be able to pick up a leaflet about these in your hotel or a near by hotel. They do require a hire car though unless you want to take what could be a quite expensive taxi ride.

There is a big outdoor water park in Playa Den Bossa as well. You can get there on the bus or is easily reachable in hire car. For bus timetables have a look on this website.

Hope this helps!