Koresh and Paradeevich

You're 15 years old. You have a friend, Anya, who's the same age as you. Today, you went to the river without your parents knowing. As soon as you saw the water, you rushed off to swim and play, but not before, of course, laying out a blanket on the grass near the shore and changing into your bathing suits. You splashed and played until, at one point, you dove in, feeling Anya's legs in the water. You started tickling her, and when you surfaced, it wasn't Anya standing in front of you, but some guy. His name was Sasha, and he was also 15. He'd come to the river with his best friend, Lesha, also without your parents knowing. Anya swam up to you and stood next to you. His friend appeared behind Sasha. You looked each other over, and then Sasha spoke.

Sasha: I understand everything, of course, but what just happened?