Auxiliary ship

[2] [3] Auxiliary ships are extremely important for navies of all sizes because if they were not present the primary fleet vessels would be unsupported.

Smaller coastal navies tend to have smaller auxiliary vessels focusing primarily on littoral and training support roles, while larger blue-water navies tend to have larger auxiliary fleets comprising longer-range fleet support vessels designed to provide support far beyond territorial waters.

[5] Oilers ("replenishment tankers") are vessels specifically designed to bring fuel oil to the fleet, while the earlier Colliers supplied coal-burning steamships.

In particular, troopships and attack transports are used to carry a large number of soldiers to operational theatres.

[8] Large ocean tugs (AT, ATO, ATF, ATA, ATR)[jargon] are used to tow large auxiliary ships, like barges, floating repair docks, and floating cranes in the open sea, also disabled ships.

[21] and barges are classified as a Type B ship or YF, YFN, YFR, or YFRN.

[23] Hospital ships are able to provide medical care in remote locations to personnel.