I did this a couple years ago and it was a lot of fun. We rent wave runners in CA, launch them at Dana Point, and then we go all the way across the channel to Catalina Island. It takes about 4 hours depending on how many rest breaks you take. The prep for this is you really need to be able to do squats for about an hour. That will usually take some time to work up to it. When you're on the waverunner, you'll be standing up and sitting down a lot. Usually we'd go fast enough that we'd jump off of one wave, jump over a wave in the middle and then come down the backside of another wave. We did that for 2 hours straight. It was amazing.
We were on the water and were surrounded by dolphins. I'm not kidding it was an area at least 300meters where dolphins were jumping all around us. It was like the seas were boiling. Some of them even followed us for a while. It was a trip!
On the island, we'll camp in Two Harbors. They have those army canvas tents with cots. So you will need to bring clothes, sleeping bag, some cooking gear and other sundries. They have a store right there by the camp so anything you forget you can buy there (like marshmallows). We can also take spears and go fishing during the day or at night. We found the hunting the best at night but that's when the sharks hunt as well so you have to be a little wary. We never went hungry, though. We ate fish tacos every day and also ended up with a lot of lobster.
For those not into the wave runner deal, there's also a ferry that can take you to the island and we'll meet you there. Lot's of fun things to do and lots of adventure as we take the wave runners around the kelp beds and see all the fish. You'll want a mask, fins, weight belt, knife, gloves and boots, and a wet suit for the snorkeling/fishing. We use a simple pole spear to catch fish (long metal tube with an elastic at one end to propel the spear in the water).
The dates are somewhat flexible but by the end of September we'll want to settle on specific days so let me know if you'd like to get on the list.