Attached are some progress images from the render. They should outline the steps I took and in which order to achieve the final render.
The main thing I want to talk about is the compositing. There is a picture of the nodes I used when compositing and it shows a lot going on. Originally I wanted to render out the foreground (characters, net, beach), the background (distant water, island, horizon line), and the sky, and the futa dicks which I could layer on top for the alt.
However there was a problem where the dicks would not look right. There was some sort of line around them that would make them look detached (see picture). There was also a similar effect that would happen around the body when against the sky. I spent a long time rendering and rerendering to try and get it to work, but it ended up being a wash.
I did learn a lot through the trail and error which I can use for future work, but I'm still a little disappointed I couldn't get it to work in this case.