Aberdeen owner Sentinel Marine is spending £36m ($46m) on three new emergency response and rescue vessels (ERRVS).
An unnamed Chinese yard is building the trio, named Cromarty Sentinel, Trafalgar Sentinel and Viking Sentinel.
The move creates 80 jobs for the owner.
The vessels will be delivered by the end of 2020.
Rory Deans, chief executive of Sentinel Marine, said: “This is a speculative investment by Sentinel Marine, based on the significant demand there has been for our fleet of high-specification custom-build vessels which we have introduced on a rolling programme since 2015.