Even if there are cliques, they may open up to new people. There will of course be other new people, too.
You can always just introduce yourself and ask if it the other person's time at the camp. If it isn't, you can ask them questions about the camp, what they like, how the food is, what to watch out for.You can ask everyone where they're from.
You can ask what they're looking forward to doing at camp. For some, it might be swimming; for others, maybe arts & crafts or nature hikes, etc.
You can always compliment someone on something they've brought with them or just ask about it.
The counselors will make sure everyone gets to know everyone, so that will help. Really, it'll all work out more smoothly than you can imagine.