ROVs
Started as simple underwater cameras with the ability to be remotely operated from the surface, the ROVs got quite an evolution in the past 30 years. Main characteristics of ROVs are the almost endless energy source provided with the umbilical cable, and the extreme flexibility (intelligence) of the human pilot on the surface. These two features allowed the development of mainly two families of ROVs: heavy-duty/deep-waters ROVs and light/shallow-waters ROVs.
Usually provided with mechanical arms or actuators, the formers are heavily used in case of deep underwater intervention where no other means are possible. The dimensions of these machines are rather relevant due to the power needed to cope with the umbilical cable's drag (at few km depth the cable length can "wag the dog"), sea currents, and mission tasks (move objects, grab samples or repair damages). Military, marine intervention companies, and of course oceanographic and research institutions, are the main producer and user of such technology. A comprehensive list of vehicles and companies can be found on the ROV Committee of the Marine Technology Society and even more details on the Rons ROV Links. Among them are companies such Perry Slingsby Systems (triton), Oceaneering International (magnum, millennium, crov), and research institutions as the Japanese Jamstek (Kaiko, urov7k, dolphin) and the American Woods Hole (Jason).
While more complex and capable machines are developed for deep waters or heavy-duty environment, is in shallow waters that a new revolution is on its way. Tired of dealing with huge, heavy and expensive machines some emerging companies are producing much smaller, light and inexpensive ROVs capable to extend even to small enterprises and little research groups or privates, the possibility
(Seamor) the English to buy, deploy and use rather sophisticated vehicle. Some companies excel among others like for example: the Canadian InuktunSeaEye (falcon, panther) and the American SeaBotix with the innovative LBV. Don Rodocker founder of SeaBotix and father of the Hyball by Hydrovision wanted a valuable and affordable ROV for everybody. The size, flexibility and prize of the Little Benthic Vehicle (LBV) are hard to beat among ROVs. Still it has to be mentioned a class by itself with the Swedish Mark III and Mark IV (Double Eagle) designed by Gunnar Wänström founder of SuTech (now part of the Saab-Bofors Group): the first Holonom ROV available on the market. In 2006, together with the guys of Ocean Modules, Mr Wänström designed the superlight OM V8 Sii, joined recently by the superlative V8 Offshore: another two excellent ROVs in the Holonom company tradition.
AUVs
The umbilical cable drag and the human dependency of ROVs are only two technical characteristics. Unfortunately there is a main economic disadvantage. For every hour a ROV is on the sea bottom, it is not only the cost of hiring the ROV and the pilot itself that set the price: a entire ship and its equipage has to be on top of the ROV for the same amount of time in order to allow working on the sea bottom. Clearly this has a huge impact on the final costs of a mission.
Whenever is possible other means are more than welcome. In the case of underwater survey where a "simple" flyby is requested AUVs are rapidly taking the place of ROVs and towed probes. Their success is due to the capability of working nearly 24h/day and to complete a survey mission (at fixed altitude, generating bathymetry maps with constant resolution) in often one third (or one fourth) of the time needed with other solutions. Moreover AUVs have been used under the North Pole ices where it would have been impossible to a ship to pursuit the robots. Thanks to the sophisticated payload and on board sensors and electronics, AUVs are so reliable to be launched and retrieved, even from a hole on the ice in the middle of the Arctic Ocean. A certain number of companies are producing and selling AUVs: among them (Maridan), ISE (Theseus, Explorer), Atlas MaridanKongsberg Simrad (Hugin 3000, c'inspector). More or less the same concept we saw with the ROVs is happening for the AUVs: there is even a class of smaller AUVs but not less technologically advanced. The first of them come directly from academic research (as Maridan) yielding very reliable and advanced product. We can enumerate the MIT blazoned Bluefin Robotics (Odyssey) recently innovating with Hovering AUVs (Odyssey IV), the very experienced Hydroid (the famous REMUS) with a remarkable 70 AUVs sold, the more recent Sias Patterson (Fetch2), the Icelander Hafmynd (Gavia) listing US-Navvy among its customers, and the newborn Ocean Server Technology's Iver2. An exhaustive list of AUVs can be found in Professor Uwe Zimmer's site and again on Rons ROV Links. 
Despite most of them develop survey AUVs few innovative companies and research institutions are designing and producing intervention AUVs: some of them has been cooperating in a 1.2 M€ EU funded "Freesub Project" (HPRN-CT-2000-00032) which already in November 2003 delivered ALIVE the first intervention AUV realized by Cybernetix. As a evolution of the proven concept the english Seebyte and Subsea7 "have joined forces to develop the next generation of AUV for the offshore oil and gas industry" as they recently stated. As we did for the ROVs even for AUVs has to be mentioned a class by its own; the only AUV capable to claim an unlimited autonomy: the solar powered autonomous underwater vehicle (SAUV II), realized by Richard Blidberg and its team at the Autonomous Undersea Systems Institute (AUSI).
With few exceptions many of these AUVs are commercial off the shelf products: most companies describe how can they custom design their product, but few modification are allowed to the main structure. Despite a good solution to this problem was suggested by Hafmynd with their patented QuickLock system installed on Gavia allowing to configure the AUV on the spot, still in these days not many companies are willing to modify their product even after having sold it. The customizing procedure takes often part only before the customer delivery. For this reason many research groups are still forced to invest a rather big amount of time and money designing from scratch their own AUV. Fortunately this condition often pushes research institution to explore new paths and consequently make significant progress in the field. Among them we can surely remember the superlatives Jamstek (Urashima) and Woods Hole (Sentry and the hybrid Nereus), togeter with smaller but not less innovative university groups spread all over the world. Some of them meet every year at the AUV Competition organized by the Association for Unmanned Vehicle Systems International or at the Student Autonomous Underwater Challenge - Europe (SAUC-E) organized by Defence Science and Technology Laboratory. A display of famous labs and their robots can be founded there.
There are many companies and research groups that produce, sell, or use, underwater robots all over the world. Given Perrone Robotics' aim to cover a wide range of undersea problematic, and particularly being the Raia Project a hybrid vehicle, it is necessary to consider both Remotely Operated Vehicles (ROVs) and Autonomous Underwater Vehicles (AUVs) in order to produce an exhaustive comparison.
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