Vessel guards

.We hear everyday of pirates ransacking ships, taking possession of oil,LPG tankers. What do we do to cripple this ? None! 

I have this wonderful idea of deploying underwater army robots to tackle such crimes. A 1.5 billion dollar ship needs to be protected. Hence, by giving command to the robots by the captain and then deploying the robots which are capable of destroying the pirate ship, the possibility of saving the crew,cargo can be done effectively .