Sonar
P.J. Westervelt summarizes the trends involved.

Sonar in extraterrestrial contexts: The use of both active and passive sonar has been proposed for various extraterrestrial environments. One example is Titan, where active sonar could be used to determine the depth of its hydrocarbon seas, and passive sonar could be used to detect methanefalls.
Proposals that do not take proper account of the difference between terrestrial and extraterrestrial environments could lead to erroneous measurements.

Ecological impact: 

Effect on marine mammals: Research has shown that use of active sonar can lead to mass strandings of marine mammals. Beaked whales, the most common casualty of the strandings, have been shown to be highly sensitive to mid-frequency active sonar. Other marine mammals such as the blue whale also flee from the source of the sonar, while naval activity was suggested to be the most probable cause of a mass stranding of dolphins. The US Navy, which part-funded some of the studies, said that the findings only showed behavioural responses to sonar, not actual harm, but they "will evaluate the effectiveness of [their] marine mammal protective measures in light of new research findings". A 2008 US Supreme Court ruling on the use of sonar by the US Navy noted that there had been no cases where sonar had been conclusively shown to have harmed or killed a marine mammal.
Some marine animals, such as whales and dolphins, use echolocation systems, sometimes called biosonar to locate predators and prey. Research on the effects of sonar on blue whales in the Southern California Bight shows that mid-frequency sonar use disrupts the whales' feeding behavior. This indicates that sonar-induced disruption of feeding and displacement from high-quality prey patches could have significant and previously undocumented impacts on baleen whale foraging ecology, individual fitness and population health.
A review of evidence on the mass strandings of beaked whale linked to naval exercises where sonar was used was published in 2019. It concluded that the effects of mid-frequency active sonar are strongest on Cuvier's beaked whales but vary among individuals or populations. The review suggested the strength of response of individual animals may depend on whether they had prior exposure to sonar, and that symptoms of decompression sickness have been found in stranded whales that may be a result of such response to sonar.  It noted that in the Canary Islands where multiple strandings had been previously reported, no more mass strandings had occurred once naval exercises during which sonar was used were banned in the area, and recommended that the ban be extended to other areas where mass strandings continue to occur.

Effect on fish: Low frequency sonar can create a small temporary shift in the hearing threshold of some fish.

Frequencies and resolutions: The frequencies of sonars range from infrasonic to above a megahertz. Generally, the lower frequencies have longer range, while the higher frequencies offer better resolution, and smaller size for a given directionality.
To achieve reasonable directionality, frequencies below 1 kHz generally require large size, usually achieved as towed arrays.
Low frequency sonars are loosely defined as 1–5 kHz, albeit some navies regard 5–7 kHz also as low frequency. Medium frequency is defined as 5–15 kHz. Another style of division considers low frequency to be under 1 kHz, and medium frequency at between 1–10 kHz.
American World War II era sonars operated at a relatively high frequency of 20–30 kHz, to achieve directionality with reasonably small transducers, with typical maximum operational range of 2500 yd. Postwar sonars used lower frequencies to achieve longer range; e.g. SQS-4 operated at 10 kHz with range up to 5000 yd. SQS-26 and SQS-53 operated at 3 kHz with range up to 20,000 yd; their domes had size of approx. a 60-ft personnel boat, an upper size limit for conventional hull sonars. Achieving larger sizes by conformal sonar array spread over the hull has not been effective so far, for lower frequencies linear or towed arrays are therefore used.
Japanese WW2 sonars operated at a range of frequencies. The Type 91, with 30 inch quartz projector, worked at 9 kHz. The Type 93, with smaller quartz projectors, operated at 17.5 kHz (model 5 at 16 or 19 kHz magnetostrictive) at powers between 1.7 and 2.5 kilowatts, with range of up to 6 km. The later Type 3, with German-design magnetostrictive transducers, operated at 13, 14.5, 16, or 20 kHz (by model), using twin transducers (except model 1 which had three single ones), at 0.2 to 2.5 kilowatts. The simple type used 14.5 kHz magnetostrictive transducers at 0.25 kW, driven by capacitive discharge instead of oscillators, with range up to 2.5 km.
The sonar's resolution is angular; objects further apart are imaged with lower resolutions than nearby ones.
Another source lists ranges and resolutions vs frequencies for sidescan sonars. 30 kHz provides low resolution with range of 1000–6000 m, 100 kHz gives medium resolution at 500–1000 m, 300 kHz gives high resolution at 150–500 m, and 600 kHz gives high resolution at 75–150 m. Longer range sonars are more adversely affected by nonhomogenities of water. Some environments, typically shallow waters near the coasts, have complicated terrain with many features; higher frequencies become necessary there.

See also: Baffles (submarine) – Areas  behind a submarine or ship where sonar cannot hear
Gordon Eugene Martin – American physicist (born 1925), sonar physicist

Explanatory notes: 

Citations: 

General bibliography: Dring, Thomas R. (March 2018). "A Steep Learning Curve: The Impact of Sonar Technology, Training, and Tactics on the Initial Years of U.S. Navy Antisubmarine Warfare in World War II". Warship International. LV (January 2018): 37–57. ISSN 0043-0374.
Hackmann, Willem. Seek & Strike: Sonar, Anti-submarine Warfare and the Royal Navy 1914–54. London: Her Majesty's Stationery Office, 1984. ISBN 0-11-290423-8.
Hackmann, Willem D. "Sonar Research and Naval Warfare 1914–1954: A Case Study of a Twentieth-Century Science" (subscription required). Historical Studies in the Physical and Biological Sciences 16#1 (January 1986) 83–110. doi:10.2307/27757558.
Urick, R. J. (1983). Principles of Underwater Sound (3rd edition). Los Altos: Peninsula Publishing. ISBN 9780932146625. OCLC 1132503817.

Fisheries acoustics references: Fisheries Acoustics Research (FAR) at the University of Washington
NOAA Protocols for Fisheries Acoustics Surveys
Acoustics Unpacked Archived 2017-09-16 at the Wayback Machine—A "how to" great reference for freshwater hydroacoustics for resource assessment
"ACOUSTICS IN FISHERIES AND AQUATIC ECOLOGY"
"Hydroacoustic Protocol – Lakes, Reservoirs and Lowland Rivers" (for fish assessment)
Simmonds, E. John, and D. N. MacLennan. Fisheries Acoustics: Theory and Practice, second edition. Fish and aquatic resources series, 10. Oxford: Blackwell Science, 2003. ISBN 978-0-632-05994-2.

Further reading: "Canada: Stable Sonics", Time, October 28, 1946.  An interesting account of the 4,800 ASDIC sonar devices secretly manufactured at Casa Loma, Toronto, during World War II. Retrieved 25 Sept. 2009.
"Radar of the Deep - SONAR", Popular Science, November 1945, pp. 84–87, 246, 250: one of the best general public articles on the subject

External links: 
FFI Facts: Sonars and the marine environment by the Norwegian Defence Research Establishment (FFI)
Remote Sensing for Coastal Management: Single Beam Sonar—Coastal Services Center, National Oceanic and Atmospheric Administration