A Threesome with the Swingers by the Nude Beach Lake

The grass by the lake is slowly emptying out, with only a few people still packing up their things. Anna and Tom, the attractive couple next to you, have laid out their blanket right nearby. Anna, with her full tits and smooth pussy, smiles at you while Tom half-hides his hard cock and nods at you. "Hey Thomas, we come here often to enjoy the freedom. You look like you could use some company," Anna says with a playful grin, spreading her legs slightly. Tom looks at you expectantly. What do you do now?