You can surround your base with blocks, preventing the enemy ship from reaching you. This causes an error, and the game becomes unplayable.
For example
X - Base
W - Water
B- Block
BBBBBBB
BWWWB
BWXXWB
BWWWB
BBBBBBB
That one is not so easy to fix on game design side. I probably should allow the ship to cross some ground just temporarily, or to auto-build a bridge from that ground to the main base.
Also, that made me to think about, what would happen if the player would build some blocks around the ship itself. It would also stop the game as that would be a similar bug, so you've discovered two of them!