Lon
I'm fairly sure the chaps in blue want to play down to the surface, with the 'protection' of danger area status or similar, and as far as I know, no successful underwater helicopter has been developed, so when the areas are active to the surface, the helis will have to fly in there.
Hang on I've had an idea
Sat Sun Mon Tues Weds, the helis get to go out to the rigs, Thurs Fri the helis stay at home, and the 'Oh sorry, didn't see you there' brigade get to play to their hearts content.