The grid doesn't help, as two subs can be a different number of squares away and hit or miss, depending on which one is going horizontally and which one vertically. The concept of the gameplay has potential, and you did get some interesting puzzles, but there are more problems than props.
The music gets stale fast, and the premise is screwed. Clean up by trashing them? Try giving them an 'enemy' skin and saying you've taken over their navigation!