Similar to a dutch rudder, except the boatsmen form an unbroken circle. Each member of the navy holds their own penis as well as the formarm of the seaman to the right of them and operate their rudder by moving their hand up and down. One member must be appointed "rear-admiral", and it is their responsibility to call out "1-2-3, row!" to guide the masturbation.
We had a 10 man Dutch Navy going on last night when the Rear Admiral called out, "FIRE THE TORPEDOES!"