The Marsdiep is the sea hole between Texel and the mainland shore of North Holland.
On All Saints’ Eve in 1170 the North Sea broke the line of dunes between Huisduinen and Texel. Texel has been an island ever since. Here, fellow countrymen on the other side are called ‘othersiders’ (mainlainders). Our compatriots from the other side call us othersiders. That’s just how it is.
Othersiders (the first variety) in particular often regard the water obstacle at hole 9 as the Marsdiep: the last dangerous sea hole before the safe shore is reached.