I think I know how to make a giant fish head stick out of your ship with heat treatment...
If you made a model of a fish head,
super heated the front of your two ships,
then pushed the model from the inside of the ship to the super heated ship surface there would appear a fish head at the front of your ship.
Depending on how far you want to go you could stick the head out a bit from the ship...
Maybe even have fins.
But the plastic would be stretched rather thin...

Im not sure what you are trying to do exsacly,
But if you want a fish head at the front of your ship you could try that.