All ships have a unique silhouette and this characteristic is often the best means of telling one type of ship from another. Here are some ship silhouettes that are representative of their type, as well as some pointers on how to tell ships apart. At sea such quick identification can be a big aid.
Typing Ships by Their Silhouettes
An incredible assortment of ships sail the planet's waters. Ranging in size from behemoths like aircraft carriers and supertankers to little fishing trawlers, making sure that accidents are kept to a minimum in an environment where the endless waters and unpredictable weather is no mean feat. Often the first step in deciding what course of action to take when two ships meet at sea is simply to figure out what the respective crews are dealing with. Identifying whether a ship appearing on the horizon is a fishing boat or cargo ship is key in ascertaining the proper attitude towards it - while a big cargo ship is likely to be relatively hard to maneuver and so can be expected to maintain a fairly predictable course, a smaller ship could well turn unexpectedly and pose a collision hazard.
But telling ships apart, even big from small, is not always easy at sea. Size can be deceptive, especially if distance is not clear. And at sea, with no landmarks or sizing clues to work with, it is easy to underestimate or overestimate the size of ships appearing on the horizon. In the Second World War it was not uncommon for scout ships and aircraft to report that they had spotted fleets full of huge battleships, only to later find that they'd seen a squadron of smaller destroyers.
To tell ship types apart in a reliable fashion, typing ships by silhouettes has become a common practice. Different types of vessels exhibit starkly differing physical characteristics that can be noted by the naked eye. From the shape of the deck to the pattern of the superstructure, silhouettes make it easy to tell a navy cruiser apart from a cargo ship.
USS Kittyhawk Operating in Support of Operation Enduring Freedom, courtesy of the United States Army, via Wiki Commons
Supercarriers are some of the largest and most visually striking ships to behold. Only eleven of them exist, all used by the United States Navy, and all are rather easily identifiable by their flat deck profile broken up only by the aircraft that are parked around it. Fortunately for anyone at sea, these 1,000+ foot, 100,000+ ton behemoths only travel when surrounded by smaller ships and covered by jets and helicopters. Passing ships will know it is there and be guided a safe distance away in short order- no one risks damage to a supercarrier.
Silhueta Navio Aeródromo - (Silhoutte ship (carrier)) courtesy of Brazilian Navy, via wiki Commons
Not ever carrier is a supercarrier - that title is reserved for the biggest aircraft carriers afloat. Many other nations operate fixed wing jet aircraft off smaller carriers whose physical profile fits the slang term "flattop" which is often applied to carriers. One or two boxy conning/flight operations towers set off to one side are pretty much the only feature above the level of the flight deck, which may also be broken up by the silhouetted of numerous helicopters and jets around the deck, a scene befitting what is essentially a mobile airfield.
Crude Oil Tanker: U.S. Navy, by Photographer's Mate 1st Class Kevin H. Tierney, courtesy of the United States Navy via Wiki Commons
Surprisingly, aircraft carriers are rivaled, within the realm of things meant to float, in size and weight only by supertankers. These nondescript, ubiquitous vessels make modern society possible by moving oil and fuel between production fields and refineries which are often separated by thousands of miles. Identifying supertankers is fairly simple - if it’s big, sits high in the water, has a substantial superstructure located far forward or aft, and doesn't seem to have distinct shapes above the main deck then it may well be a tanker. The lower in the water it appears to be the more heavily laden with liquid it probably is.
Laden Cargo Vessel in a Washington Port, courtesy of Wiki Commons user Rootology and via Wiki Commons
Tankers may carry society's lifeblood- fuel- but cargo ships carry everything else of value that is heavy and shipped in bulk. While airplanes get there faster, cargo ships carry far, far more and remain the most economical means of moving goods over long distances. When loaded, cargo ships are easily identified by the towers of shipping containers stacked on their deck. Their profile sits high even as their hull sinks low in the water. What superstructure they have is minimal and set to the front or rear of the ship.
The problem, as far as identification goes, comes when they aren't loaded. When it comes to telling the types of ships by silhouette, an empty cargo vessel and tanker look very much alike. Fortunately, it isn't profitable to send empty cargo ships out to sea. In most cases, even if they've just offloaded a massive number of shipping containers from a distant port, they're getting ready to load some more for transport to their next destination. And in truth, both tankers and cargo ships are so large, loaded or not, that it is best to keep clear.
Cruise Liners Silhouette - Side View, courtesy Wiki Commons user Marcusroos and via Wiki Commons
Cruise liners are found all over the world, but especially in places where tourists like to visit. They frequently travel up and down coastlines and can be a problem when coming into a major port. Fortunately they are usually large and quite tall, being effectively floating hotels. Look for a continuous superstructure as the most telling feature.
USS Iowa with Christmas Decorations, by PH1 Jeff Hilton, courtesy of the United States Navy and via Wiki Commons
Battleships are an unlikely sight at sea, since only four remain in existence (save for museum pieces) and only two, owned by the United States, could be made seaworthy in a crisis. But just in case, battleships can be told apart from other vessels by their sheer size (rivaling carriers, tankers, and cargo ships) and above all by the big cylindrical tubes that stretch out from the main body of the ship. As the above image aptly demonstrates, even when a battleship is as close to looking like a solid mass against the horizon as it can get, some of those gun barrels stick out. They're almost a foot and a half in diameter and in better viewing conditions can be seen to be attached to massive turrets located along the vessel's central axis.
The Soviet-era Battlecruiser Kirov, by PH Beech, courtesy of the United States Navy and via Wiki Commons
The battlecruiser is mostly a forgotten breed, but several ships that could ostensibly be claimed to be battlecruisers are operated by Russia. These revamped members of the Kirov class are nuclear powered and house twenty massive cruise missiles plus a couple hundred surface to air missiles forward of their superstructure. The relatively streamlined superstructure, small guns and helicopter pad aft, sharply rising bow, and long flat area forward of the superstructure is the dead giveaway that this is a Kirov.
USS Bunker Hill on Patrol by Mass Communication Specialist, 2nd Class; James R. Evans, s
courtesy of the United States Navy via Wiki Commons
Only the United States Navy and Russian Navy still operate cruisers in significant numbers, and they look quite a bit different. The US operates many more than even Russia though, and while Russia's look a lot like smaller Kirov class battlecruisers or oversized destroyers, US cruisers of the later variants of the Ticonderoga class are distinctive due to their long superstructure bookended by large boxy sections fore and aft and featuring an old-school tripod mast in between. This shape allows them to mount vertical launch systems for missiles fore and aft and the Aegis defense system to control them. This system is characterized by the hexagonal panels located on flat surfaces of the superstructure. This system incorporates long range radar and an automated combat control system.
Guided Missile Destroyers
Type 42 Destroyer of the British Royal Navy, courtesy of Wiki User MoRsE and via Wiki Commons
Guided missile destroyers (often abbreviated DDG) are used by many navies as their primary surface combatant: they are powerful vessels capable of controlling air and sea in the service of the navies that operate them. American and Japanese DDGs are distinctive in that they look a lot like Ticonderoga/Bunker Hill type cruisers, and have boxy superstructures that house the Aegis system. Other navies follow a pattern more like the silhouette above, with a couple mid-caliber guns located fore and aft and a surface to air missile launcher or two set up very close to the long superstructure. They often have a helicopter pad aft as well, and a fairly streamlined appearance.
Russian Federation Navy Destroyer of the Udaloy Class: Marshal Shaposhnikov, on a Visit to Pearl Harbor, by Photographer’s Mate 1st Class William R. Goodwin, Courtesy of the United States Navy and via Wiki Commons
Many destroyers are specialized submarine hunters, and dispense with the Aegis-type systems and surface to air missile launchers in exchange for a hidden punch: high tech sonar systems and enlarged helicopter facilities. Often they have only self-defense weapons to ward off aircraft and ships, but as sub-hunters they are second to none. Indeed, a pair of anti-submarine destroyers operating in tandem, especially if backed up by a pair of helicopters, is every submariner's worst nightmare.
They are particularly distinctive due to their clean lines - the Udaloy class destroyer pictured above is a bit cluttered relative to other modern designs. The Spruance class of the United States, for example, was criticized for not looking dangerous or well-armed enough even though the members of this class were among the best sub-hunters of all time.
USS Sacramento Resupplying a Carrier Battle Group by Photographer's Mate Airman Chris M. Valdez, Courtesy of the United States Navy and via Wiki Commons
The warships may attract all the attention, but without the aid of dedicated replenishment ships, they rapidly run out of beans, bullets, and gas on long cruises. Navies with global reach only maintain that reach by deploying a fleet of replenishment vessels that carry needed essentials to the warships.
These vessels are quite easy to distinguish when silhouetted against the horizon because of their busy decks. They have any number of protruding hawsers, hoses, and cranes along the edge of their decks and it is not uncommon to see larger bulk items stored above the deck as well. Even if these features were not enough to set them apart from cargo ships, many are equipped with a helicopter pad as well- not a common sight on civilian cargo decks.