depends where you are staying,but i think you can go from san an to san an,but it does not go right round the island,or ibizatown to ibizatown,,,so best to get aferry boat from san to ibizatown and back,,,nice ride if not ruff sea..should be a nice 4 hours or more out..stops at all resorts on the way there.and back,you sometimes have to change boats to a bigger one,depends how many are waiting for them.
you could hire one for the day? private boat full crew