You decide that since the creatures in the water definitely don't look like piranhas, you will most likely be safe if you chose to take a swim. Especially after running that much. You just realised. You are VERY dirty.
You take off your clothes and place them aside a fair distance, not too far, and you go up to the lake. You dip your toe in the water for a moment, then lift it up. Nothing. The water's fine. You step into the water, slowly moving further in so you are standing about belly deep.
The creatures you saw have noticed you, and they swam over to you. While they aren't coming closer, they don't seem like they will leave soon enough.