For those who wish to begin a draining exercise, fist fill the duct.
This can best be done with a boat full of people.
First go ahead into a very narrow and shallow creek.
When the skeg touches the bottom, raise the engine to about 45 degrees.
It helps if the engine then fails to engage reverse.
When reverse is finally selected, increase the throttle setting until there is a mixture of water and foam spilling over the transom.
The captain should, at that point be so concerned about avoiding other floaty things that he completely fails to notice the water and foam coming aboard.
When the issue is pointed out to him by the crew, he shouts at the crew and insists that everything is OK.
Water around the ankles is the first indictaion to the captain that, maybe, all is not well.
This exercise is also best done in a harbour with a low speed limit ( see thread on Cowes, for example) where the elephants trunk is ineffective.
When all aboard have wet feet, socks, trousers and are the picnic is also soaked, find a pub which welcomes such a crew!
On return home, remove the carpets from the car so that they can dry out!