Baldeep,
WE HAVE A MARITIME PATROL AIRCRAFT!!! The Merlin is superb at this role - speak to the guys and gals at a secret airbase in Cornwall. It is the dogs danglies and really rather competent at this role. The fixed wing brethren need to understand that they do not have a monopoly on ability or effectiveness. Need supplies delivered to a mountain site in Afghanistan? Answer...rotary. Want rescuing? Rotary. Need some bad men killed at close quarter? Rotary (AH - anyone care to argue?!). Need a maritime aircraft that can move with the fleet and kill subs - ...you know the rest...
I'm not qualified to discuss the merits of rotary vs fixed wing. Is a helicopter as defendable when the chips are down though, in the maritime role?