Tugboat

Fleet tug USS Tawasa (1,255 tons, 205 ft) which towed a nuclear depth charge as it was detonated in Operation Wigwam in 1955

Tug and barge connected

Seagoing tugs (deep-sea tugs or ocean tugboats) fall into four basic categories:

1. The standard seagoing tug with model bow that tows almost exclusively by way of a wire cable. In some rare cases, such as some USN fleet tugs, a synthetic rope hawser may be used for the tow in the belief that the line can be pulled aboard a disabled ship by the crew owing to its lightness compared to wire cable.
2. The "notch tug" can be secured by way of cables, or more commonly in recent times, synthetic lines that run from the stern of the tug to the stern of the barge. This configuration is generally used in inland waters where sea and swell are minimal because of the danger of parting the push wires. Often, this configuration is employed even without a "notch" on the barge, but in those cases it is preferable to have "push knees" on the tug to stabilize its position. Model bow tugs employing this method of pushing nearly always have a towing winch that can be used if sea conditions render pushing inadvisable. With this configuration, the barge being pushed might approach the size of a small ship, with the interaction of the water flow allowing a higher speed with a minimal increase in power required or fuel consumption.
3. The "integral unit", or "integrated tug and barge" (ITB), comprises specially designed vessels that lock together in such a rigid and strong method as to be certified as such by authorities (classification societies) such as the American Bureau of Shipping, Lloyd's Register of Shipping, Indian Register of Shipping, Det Norske Veritas or several others. These units stay combined under virtually any sea conditions and the tugs usually have poor sea-keeping designs for navigation without their barges attached. Vessels in this category are legally considered to be ships rather than tugboats and barges must be staffed accordingly. These vessels must show navigation lights compliant with those required of ships rather than those required of tugboats and vessels undertow.
4. "Articulated tug and barge" (ATB) units also utilize mechanical means to connect to their barges. The tug slips into a notch in the stern and is attached by a hinged connection, becoming an articulated vehicle. ATBs generally utilize Intercon and Bludworth connecting systems. ATBs are generally staffed as a large tugboat, with between seven and nine crew members. The typical American ATB displays navigational lights of a towing vessel pushing ahead, as described in the 1972 ColRegs.

Svitzer Tyr, a Danish tugboat, built in China in 2011, pictured in 2018 in Ystad harbour

Compared with seagoing tugboats, harbour tugboats that are employed exclusively as ship assist vessels are generally smaller and their width-to-length ratio is often higher, due to the need for the tugs' wheelhouse to avoid contact with the hull of a ship, which may have a pronounced rake at the bow and stern. In some ports there is a requirement for certain numbers and sizes of tugboats for port operations with gas tankers.[2] Also, in many ports, tankers are required to have tug escorts when transiting in harbors to render assistance in the event of mechanical failure. The port generally mandates a minimum horsepower or bollard pull, determined by the size of the escorted vessel. Most ports will have a number of tugs that are used for other purposes than ship assist, such as dredging operations, bunkering ships, transferring liquid products between berths, and cargo ops. These tugs may also be used for ship assist as needed. Modern ship assist tugs are "tractor tugs" that employ azimuthing stern drives (ASD), propellers that can rotate 360 degrees without a rudder, or cycloidal drives (as described below).

River tug pushing a log raft in British Columbia near Vancouver (May 2012)

River tugs are also referred to as towboats or pushboats. Their hull designs would make open ocean operations dangerous. River tugs usually do not have any significant hawser or winch. Their hulls feature a flat front or bow to line up with the rectangular stern of the barge, often with large pushing knees.

The Kort nozzle is a sturdy cylindrical structure around a special propeller having minimum clearance between the propeller blades and the inner wall of the Kort nozzle. The thrust-to-power ratio is enhanced because the water approaches the propeller in a linear configuration and exits the nozzle the same way. The Kort nozzle is named after its inventor, but many brands exist.

The cycloidal propeller is a circular plate mounted on the underside of the hull, rotating around a vertical axis with a circular array of vertical blades (in the shape of hydrofoils) that protrude out of the bottom of the ship. Each blade can rotate itself around a vertical axis. The internal mechanism changes the angle of attack of the blades in sync with the rotation of the plate, so that each blade can provide thrust in any direction, similar to the collective pitch control and cyclic in a helicopter.

Theodore Tugboat, the titular hero of a children's show, was popular enough that a fullsize replica was constructed

To date, there have been four children's shows revolving around anthropomorphic tugboats.

• In the late 1980s, 13 episodes were made of TUGS, a series depicting the life of tugboats in the 1920s.
• An American adaptation using edited footage from Tugs followed: Salty's Lighthouse.
• In the 1975's Soviet short animation musical film В порту/ In the sea port a tugboat sang a song: "Through a harbour area"
• One of the creators of Tugs went on to direct Theodore Tugboat.
• Animated preschool series Toot the Tiny Tugboat started broadcasting on Channel 5 Milkshake! in 2014 and on Cartoonito in 2015, with a Welsh-language version airing on S4C Cyw.

"Tugger" is a tugboat in the animated series South Park. He appears in the episode "The New Terrance and Phillip Movie Trailer" as a sidekick for Russell Crowe in a fictitious television series entitled Fightin' Round The World with Russell Crowe. Tugger follows Crowe as he engages various people in physical conflicts, providing emotional support and comic relief. At one point Tugger even attempts to commit suicide, upon being forced to hear Russell Crowe's new musical composition.

(Alphabetical by author)

• The children's book Scuffy the Tugboat, written by Gertrude Crampton and illustrated by Tibor Gergely and first published in 1946 as part of the Little Golden Books series, follows the adventures of a young toy tugboat who seeks a life beyond the confines of a tub inside his owner's toy store.
• The Dutch writer Jan de Hartog wrote numerous nautical novels, first in Dutch, then in English.
  • The novel Hollands Glorie, written prior to World War II, was made into a Dutch miniseries in 1978 and concerned the dangers faced by the crews of Dutch salvage tugs.[16][17]
  • The novella Stella, concerning the dangers faced by the captains of rescue tugs in the English Channel during World War II, was made into a film entitled The Key in 1958.[18]
  • The novel The Captain (1967), about the captain of a rescue tug during a Murmansk Convoy, sold over a million copies.[19]
  • Its 1986 sequel, The Commodore, features the narrator captaining a fleet of tugs in peace-time.
• Little Toot (1939), written and illustrated by Hardie Gramatky, is a children's story of an anthropomorphic tugboat child, who wants to help tow ships in a harbour near Hoboken. He's rejected by the tugboat community and dejectedly drifts out to sea, where he accidentally discovers a shipwrecked liner and a chance to prove his worth. This story was animated as part of the Disney movie Melody Time.
• Farley Mowat's book The Grey Seas Under tells the tale of a legendary North Atlantic salvage tug, the Foundation Franklin. He later wrote The Serpent's Coil, which also deals with salvage tugs in the North Atlantic.