Party ideas for around a lake?

Ok, so I'm hosting a party with my neighbor who is in my homeroom in school and this summer we are inviting everyone we know to a party. Mostly everyone in our homeroom. Our houses are around a lake and there is sand there and an island and we were going to have volley ball on the island. You have to get a boat ride there though. I need food ideas for it, and activities. We are also swimming in the lake so and games for in the water would be fine too. We already thought of jumping of the boats. Were also kayaking, playing soccer, run the bases, karaoke, and dance competitions. Oh, and I need good songs for the list of songs for karaoke. Thanks!