The fighter is quite good, particularly the front of it, though you'll want to push things 1 closer together so you don't have the gap in the middle. Also, your shading on it is backwards, the higher up sections should be lighter while the lower ones should be darker, imagine shining a light on the ship from above.
As jwa said the kraken's front, spikey part is actually quite nice. The rest of it suffers from various problems already mentioned (messiness, mixing, poor section usage, etc.)
The crab ship isn't bad though in my opinion it's a step down from the fighter. The biggest problem it has is the claws. The front claws look kind of tacked on, a bit messy and they just don't really fit. The back claws are angled too steeply so they look even more tacked on and awkward, they really mess up the flow. The ship would probably look better if you removed the claws but left the connecting arms, though of course it'd be more ideal if you made something to replace the claws instead of just removing them.
Still, your ships are certainly coming along, keep at it
