Possibilities of lidar detection of fish and plankton are overviewed on cited results of nature experiments in the sea. Volume-backscattering coefficients for the lidar with wave-length 532 nm and the acoustic sonar are compared for schools of some fish species. Examples of effective detecting of fish schools and assessment of their abundance by lidar are demonstrated for cases of sardine and anchovy at California coast, capelin and herring in the North Pacific, mullet at the west coast of Florida, juvenile mackerel in the coastal Atlantic waters of southern Europe, menhaden in the Chesapeake Bay, and others. In some experiments, the per-kilometer costs of airborne lidar surveys are estimated as 10 % or less as compared to ship-based sampling. Besides, the lidar surveys take a shorter time and their results are not distorted by avoidance behavior of fish caused by ship and sampling gear noises. Experimental surveys of thin scattering layers (probably formed by plankton) made by NOAA fish lidar are overviewed, as well, including the first tests of the system in the South California Bay in April 1997, the tests in the North-West Atlantic at Iberian coast in August-September 1998, in the Gulf of Alaska in July-September 2001 and May-August 2002, in the Norwegian Sea in July 2002, in the North-East Pacific at the coast of Oregon and Washington in July 2003, and in the Gulf of Alaska in July 2003. Some aspects of future development for improvement of school-detecting capabilities of lidar are discussed, as additional scanning for 2D-images and adding of second receiver co-polarized with the laser light for better identification of fish species and other scatterers in the sea.