A great deal of this confusion is due to the lack of clear cut jurisdictional responsibilities by various agencies. Ideally , the local police should undertake marine policing upto 3 kms into the sea , from there up to 50-100 kms ( depending on what's the international practice or if we've evolved our own protocols ) should be the remit of the ICG & anything beyond that should be the remit of the IN .
This strategic loophole was exposed during the 26/11 attacks & all the protocols & measures deemed necessary started being enacted & executed . The Centre has , by & large fulfilled it's responsibilities by enhancing the role of the ICG thereby leaving the IN free from policing duties . However most of the states have failed to discharge their responsibilities by setting up a separate marine police component . With the result , the ICG & the IN are still further burdened by policing duties immediately off the coast which ideally in any other geography is the remit of the local police.
All this stems from a lack of a National Security Strategy , something the ex CoAS Gen Narawane pointed out recently.
The RN example doesn't hold as they're legitimately short of capital ships due to budgetary constraints to securitize their various overseas territories . Hence the deployment of an OPV which is good for patrolling . What happens in case of a conflict is anyone's guess. Refer to the recent imbroglio they had with Iran where in response to the RN capturing , boarding & detaining members of an Iranian vessel in the Mediterranean , the Iranians retaliated reciprocating the same action in the Persian Gulf. Would this have happened with adequate deployment of assets of the RN in the Persian Gulf ?