There are a variety of activities in Maui. Shopping can be a wonderful past time, with the abundance of shops and markets. The markets are very interesting and if you are looking for handmade artifacts the markets are the places to shop. The trip is approximately half an hour out and the bonus is whale watching. Chances are good to spot some these large marine mammals while on your way out to the crater.
Lunch is available on the boat as well.
If it is your first time at this fun water sport, the guides will provide a short training session. Then its time to jump off the boat into the warm, blue waters. Depending on the tour you book the water time varies. There are half and full day excursions. I suggest the half-day trip.