Sorry for the long time taken to reply, I have a weird work schedule...
Thank you very much for the nice comment. To answer your question : no, I didn't make the drawings from scratch, I started with photos of statues of Poseidon and of tridents, mixed them up together until I had something that pleased me, then used the result as a model in Illustrator to redraw the lines I wanted on top of it. I then made the same with photos of tentacles / octopussies for the background.
After that, it's just a little bit fun time with photoshop.
I hope my answer was clear.