Assume a slower moving boat which fires quick boats forward. In that the 'bullets' would interact with the pattern first, you have a possibility of the things destroying everything in the path of the slow boat. Could work, but the boat itself would need to destroy everything in its path.
As far as specific patterns that are just generally resilient, Life patterns tend to be pretty fragile, and I would expect this to be an unavoidable consequence of the game's rules, one that would scale to any complex construction you built.
Also, I'm not going to attempt a proof but it sure seems that for any pattern X, you could construct a (pretty simple) pattern Y than would destroy it.