Yep
Just like the others said, you can wear a tampon while in and around the lake. Like Jen mentioned, the water will actually stop your period, but many girls wear a tampon if they are going to be around the water for the simple reason that if they are not going to be in the water 100% of the time, their period will start back up again shortly after they are out of the water. You wouldn't want to necessarily take that risk, but that's up to you.
If you don't wear tampons though, I'm not sure what you could do as far as swimming goes while you were there. If that was the case, I'm not sure if there is another way you can go swimming without wearing one.
Hope this was helpful! Talking to your friend about it is another good option, it can be helpful to have someone there who knows what's going on in case you need a buddy that knows how to help you(if say... you thought something leaked for example). Good luck!
~Angelica