Ok, I said it and yes, it sounds pretentious rent a boat in Capri. The truth is that, appearances aside, it's quite doable to rent an affordable luxury speed boat to tour the storied isle.
I did this recently through Capri Boats. For about 800 Euros (around $1,150) you can rent a motor boat with a driver-guide for up to eight hours and plan out a unique tour of this famous island off Italys Amalfi Coast. The cushy speed boat comfortably accommodates four people, with room for as many as eight passengers. With friends, it's possible to split the cost and each pay as little as 100 euros (about $140) per day. Public wooden boats (youll see them in Capris marina) provide a less glamorous, more practical way to explore by water, but the private option is quite affordable and the most flexible.
The benefit of touring Capri by boat is not only that you can take in vistas of soaring cliffs, beautiful inlets, and one charming lighthouse, but also that you can stop and jump into the blue-green crystal clear water at any time. There are some tourist spots that are quite popular, including the famous blue grotto (I still don't quite understand how the water inside the cave is illuminated blue) and the lesser-known green grotto. Note that getting into the blue grotto requires transferring to a small wooden boat (for a low fee), and the boater will then take you inside the cave. Beware, the waters rise and fall at the entry; if you aren't looking and ready to fall fast on your back in the boat, you just might knock your head on the rocks because the cave's entry is so small be careful! I'm still wondering why the guide didn't warn us. Fortunately, we were looking ahead. What I didnt expect was the large splash of water that damaged my video camera; it's best to leave electronics in the speed boat.
On the tour, ask about stopping by the Faraglioni Rocks for lunch at one of the famous seaside restaurants; the island has several worthwhile spots. We instead went to another island located 10 minutes across from Capri. The lovely restaurant served the most delicious marinated sardines, grilled fish, and pasta; wash it down with a local rosé. If you eat around the rocks of Faraglioni, take a walk up about 100 steps and then 10 minutes on flat ground to the famous Capri Piazzetta, where the town is. Most people dont realize that Capris main square is located high above the sea level. Sure, you could also wait in line and take a funicular up, but why not walk (assuming you are ready for a climb) and work off the lunch? Spend an hour enjoying the town of Capri itself, then head back down to your private boat and ride back to the marina.
Note that the best way to reach Capri is the hydrofoil from Naples, about a one-hour ride. It's pretty cheap and easy, so I recommend taking this over to Capri and back. You could also take the private speed boat over to Naples or, for that matter, anywhere along the Amalfi Coast (Positano, Sorrento, etc) but expect to pay extra for fuel (there is no fuel charge for Capri-only rides).
Finally, one last reason to tour Capri's coast by boat is because there aren't any real beaches. Some hotels have jetties over the rocks, but dont expect any wide, sandy beaches here. That makes a boat tour around the isle not only special but also practical, whether you are staying overnight on Capri or just visiting for the day.