Keep swimming...

You swim on, and at first it looks like there’s nothing there, just trees overhanging the water. As you go a little further though, you can see little sandy breaks in the trees, like mini-beaches. You wish you’d known about these when you first came in, you could’ve come here instead of the main beach. It’s all shaded, but you wouldn’t’ve had to deal with the frat bros. You swim on a little further, and as the next mini-beach comes in to sight, you can’t believe your eyes.

It’s your sister, a guy and a girl nude. You stay low in the water, and move in behind some rocks so that you can observe without being seen. Getting a little closer, it’s definitely your sister, and some guy and girl you don’t recognize.

Rachel is lying on her back between the other two, her tiny titties poking up just slightly. The other two are on their back. The girl is average in height, but quite curvy. Not quite chubby, but definitely soft and curvy. She has very curly read hair that doesn’t seem to past her shoulders. Your sister’s slightly less curly brown hair is just a little longer. The girl clearly has very large breasts, as you can see them ballooning out the sides of her body as she’s lying on them. Her butt is pleasingly round, a little bigger than yours, but just as shapely. The guy has short light brown hair, is quite skinny, and somewhat tall.

“Hey Dave, can you pass me the sunscreen?” The red head says, as she moves on to her side facing away from you, and reaches over Rachel, resting her hand on Rachel’s stomach.

Dave rolls on to his side facing the two of them, and you can see his respectably sized tool. The red head takes the sunscreen from Dave, and sits up to apply it.
“Do you need some help there Monica?” asks Dave, his tone letting her know he isn’t serious.

Monica just laughs and shakes her head. Her breasts really are huge. You were right initially, the girl is soft, but not fat, and her breasts, which defy comparison, aren’t the hideous, fatty things you sometimes see. They definitely hung, rather than sticking out, but her nipples, which are flat and pink, still point out, rather than down.

She applies the sunscreen to her stomach and legs, and then her upper chest, and finally, starts working it all over her breasts. Then she lies down on her back, and so does Dave. You can’t decide whether to approach, and try to explain to them how it is that you’re out here at the beach, completely naked, spying on them from the water, or you can just continue to watch to see what they do.