Very creative ideas you've got so far
In my own opinion I think the 'top' part of the creature feels a little odd just flopping backward like that, but I don't know if these people live in the water still or outside in a gaseous atmosphere.
The ships are a great idea, although I think the two parts are a bit too contrasted to eachother in the sense that one part has a very organic feel to it while the other half still retains a strong machined look eventhough it has organic shapes and lines. Perhaps if you worked to blend the two together more you will have a more cohesive concept. Awesome work so far; love the ideas.