Using some PVC and a few floats you could mount your Red / Green markers about 35' apart and the Stern light about 100' back. That outta make em move over!
"Ship, correct your course by 20 degrees port."
"No, You correct your course 20 degrees starboard."
"I repeat correct your course 20 degrees port."
"I am the Captain of a Battleship, Divert your course."
"I am the keeper of a light house, your call."
"Ship, correct your course by 20 degrees port."
"No, You correct your course 20 degrees starboard."
"I repeat correct your course 20 degrees port."
"I am the Captain of a Battleship, Divert your course."
"I am the keeper of a light house, your call."