After some thought ,the only real choice is a chopper, twin turbine of some sort.. On something 140' those large vtol would be a problem. And from your description of using it to supply and also transport you from off shore a sea plane ,especially those single engines ones don't have hardly any usable load with full fuel. Singles with full fuel might have a usefull load of 300 to 500 pounds.Thats only a pilot and passanger and a couple cases of wine
and only do 150 to 200 knots at best.
I see alot of those sikorsky s-76's flying corperate guys, they fly fast at about 175 mph for 450 miles. One quick refuel and you have a 900 mile range.Most small corperate jets only fly that far all though a little faster.I don't know what the usefull load is but they have quite a bit of power. I did my pilot training in a aerospatial tb-9 and thos S-76 used to blow my doors off
those tb-9's did 120mph red lined
