This poster represents the Deep One city below Devil's Reef, as briefly described by H.P. Lovecraft in his masterful story 'The Shadow Over Innsmouth'.
H.P. Lovecraft is appealing to illustrators for several reasons. Firstly, his stories are extremely popular with fans of unusual fiction at present, and secondly, his descriptions of most locations and monsters are so obtuse that almost any drawing or painting can somehow fit!
You can hardly see the half-human frogmen in the small image below. But they are there.
I produced a large, 1m20 x 70cm one-off acrylic painting based on this design. This was an enjoyable one to paint, and the Amsterdam range of acrylics provided some great sea tones. The picture was on display at the WFC2013.