Rule 24

	If the length of a tow is greater than 200m, the tug and tow will display a black diamond shape. If the tow is less than 200m, the relationship between the two vessels is obvious and no signal is made.
If the tug is restricted in its ability to manoeuvre, it will display a ball, diamond, ball shape (Rule 27). This is in addition to black diamond for a tow greater than 200m, if it is required.
	Vessels towing, show side lights and towing lights, which have the same characteristics as masthead lights. Plus a yellow towing light above the sternlight. (YELLOW OVER WHITE-TOW LINE IS TIGHT!)
Two masthead towing lights mean the tow is less than 200m in length.   Three masthead towing lights mean the tow is greater than 200m in length.
	Vessels being towed, show the same lights as a sailing boat (Rule 25).

Part (g) of this Rule covers semi submerged objects.

Occasionally you will come across vessels towing objects which can not be easily lit or marked (such as pipes for the oil industry), if they are they lit they may only have the white lights shown in the last two examples above.

A dracone is a large sausage shaped bag used for transporting fluids which will float, such as oil or fresh water.

Test on Rule 24.