Tunnel thruster

A bow thruster tunnel is a channel cut into the hull of a
vessel to house a bow thruster. The tunnel is usually located at
the bow of the vessel, just below the waterline, and is designed to protect
the thruster from damage caused by obstacles in the water, and
with grids at each entrance to prevent infiltration, such as rocks and
floating debris. The bow thruster tunnel is generally made of
polyester or reinforced composite materials, and is designed to withstand the forces of the water and the pressures exerted by the thruster when in operation
.