Bluewater experience is loosely defined as experienced gained by participation in extended offshore passages in larger vessels out of the sight of land for many days.
For example: Using your 20 foot runabout to go 10 or 20 miles offshore to your favourite fishing spot does not qualify as Bluewater experience, even if you spend the night offshore.
A TransAtlantic passage to the Mediterranean Sea via Bermuda would qualify as Bluewater Experience. You would be familiar with ship’s routine, stand watches, make meals, prepare for and experience bad weather, possibly make repairs underway and deal with day-to-day items involving vessel management and upkeep.
The major difference between the two examples are the distance involved, the number of days and the exposure to a significant difference in self-reliance.