Wikipedia
L-drive
An L-drive is a type of azimuth thruster 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. 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.
The Voith-Schneider marine propulsion system (also mechanically linked) can also quickly change the direction of thrust.