An L-drive is a type of azimuth thruster

Azimuth thruster

An azimuth thruster is a configuration of ship propellers placed in pods that can be rotated in any horizontal direction, making a rudder unnecessary...

 in which the pod-mounted propellers are driven mechanically rather than electrically. Azimuth thruster pods can be rotated through a full 360 degrees, allowing for rapid changes in thrust direction and eliminating the need for a conventional rudder

Rudder

A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...

. This form of power transmission is called a L-drive because the rotary motion has to make one right angle turn, thus looking a bit like the letter "L". This name is used to make clear the arrangement of drive is different from Z-drive

Z-drive

A Z-drive is a type of marine propulsion unit. Specifically, it is an azimuth thruster. The pod can rotate 360 degrees allowing for rapid changes in thrust direction and thus vessel direction...

The Voith-Schneider

Voith-Schneider

The Voith Schneider propeller , also known as a cycloidal drive is a specialized marine propulsion system . It is highly maneuverable, being able to change the direction of its thrust almost instantaneously...

marine propulsion system (also mechanically linked) can also quickly change the direction of thrust.