Well you can play volleyball one tent v the other. Or some card game maybe. Loser(s) to stay naked for a day till next game. And so on.

Ideas
 

I like the idea of the lazy River. Try to take off your bottoms, leave them somewhere and make it all the way round back to them. You could try the same with your top, if you have something big enough to hide behind.

When queueing for one of the slides, take out your boobs and lean over the side of the railing, noone will see from nearby, but you might be exposing yourself to everyone below.

Ride every slide on your bare ass and don't adjust your bikini until you get to the bottom.

Put your valuables in a friend's bag and when you leave "lose" your locker key, so you have to get home in your bikini or towel.

Have fun,
Alice ;)

Thanks for answering! Ok so some more ideas:

Water park (but links to camping)
While at the water park, try to obtain someone else's swim-wear (how you do this is up to you, steal it, try to get items from lost property, try to buy it from them, or any other way you can come up with- this can include friends you go there with) when you go camping, you can't take your own swimming costume and can only take items you managed to collect. If you didn't collect anything then instead you have to try and borrow swim stuff from your friends at the camp.

Camping
Tell each of your 3 best friends that you lost a bet, and they can each give you a dare you have to do while on the camp.
Play a game of volleyball wearing as few items of clothing as possible
Flash every other member of your team (can be all at once or separately) you can try to make it look accidental or just own it
Sleep nude every night you're there, on the last night lie on top of your sleeping bag (either wait until everyone else is asleep, or say you're too warm)
Try to convince other members of your team to go streaking or skinny dipping
Every time you play a game of any kind, make a bet with one of your friends/ the other member of the team- try to make the forfeit/ loser's task as embarrassing as possible, at least once a day you must lose on purpose.
Through the above dare or some other means, get someone else sleeping in your tent to give you a spanking- ideally with everyone else in the tent watching.

Here's a crazy one!
Go to one of the do-it-yourself carwashes with a friend/teammate, probably later at night. One of you should then spray the other down (from a safe distance, obviously) with the hose gun, then rub their body with the foaming brush, getting them totally sudsy, before rinsing them off. Easy mode is the washer fully dressed, washee in a one piece swim suit. Medium is bikini for washee (and washer, if she wants), hard mode is wearing as little as the washee dares!
Have fun, and full report please!