Bomb "Glitch?"
 

Don't know if this is a glitch or not, but I think it's pretty cool.
I was fighting QAR and we boarded, and then one of the enemies ran off the ship for a while, so we could not continue to the next wave. I was bored so I pulled out my grenades and started chucking siege across to other ships. I then heard a mighty BOOM! I wondered what had happened so I tossed another siege at the ship, and the boom sounded again. I thought I knew what was happening so I switched to fire bomb. I threw it at the side of the ship and it exploded. I then emptied most of my siege and fire bombs into the ship. Must have been driving the crew bonkers! :peopirate07bouncele

I wouldn't say this is a glitch, it is just what happens when a grenade hits a solid object.