On the calm waters of the Mission and San Diego Bays, you can water-ski and wakeboard, dash around on a Jet-Ski, or just cruise offshore in a speedboat.
Seaforth Boat Rentals (888/834-2628, www.seaforthboatrentals.com , $35–145) has three locations: in Mission Bay , downtown San Diego , and Coronado. If you’re planning to cruise, rent one of the large (up to 240 horsepower) speedboats, which has plenty of room for passengers, coolers, and snacks.
If you’ve got an athletic crew with you, reserve a ski boat. They come with wakeboards, ski tubes, skis. For a more motorcycle-like on-the-water experience, pick up a modern, powerful Jet-Ski that rides 2–3 people.
Another multi-boat rental outfit with several locations in and around San Diego  is Action Sport Rentals (858/581-5939, www.actionsportrentals.com , $95–150). Rent yourself a three-seater Jet-Ski or a six- or seven-passenger speedboat and tool around the bays. For a bigger party, Action offers 13-passenger power pontoon boats.
If you want to water-ski or wakeboard but don’t have anyone to drive the boat, reserve some time with Action’s professional driver. You’ll get rides on whatever type of toy (wakeboard, skis, kneeboard, tube) you want behind their competitive-class ski boat.