4098 Manta cruiser
This build works as a submarine or spaceship. It is based on a fish-like shape. There is still some freedom with regard to the length of the tail. I prefer this 'longtail' version best. Although I love the shape of this model, the bottom view is not as good as it could be. There are always limitations if you stick to the available bricks of the set alone. Fortunately the bottom half is not the part from which you will looking at this model most of the time.