Bathymetric LiDAR, which is used for hydrographic applications to survey coastlines and shallow waters, operates on a different wavelength to topographic LiDAR, which uses laser pulses that are absorbed too rapidly by water to be of use. Bathymetric LiDAR sensors output laser light using the green wavelength of 532 nm, requiring a higher power which means a lower pulse rate and fewer measurements per second.
Bathymetric LiDAR drones fly lower than topographical LiDAR UAVs due to the differing laser powers and attenuations in water and air. Bathymetric LiDAR systems are typically heavier than topographical LiDAR, and so require heavy-lift multirotor drones to carry them.
UAV LiDAR bathymetry is used in coastal surveys to characterise the land and seafloor, for environmental monitoring and coastal reef mapping, to gather data for flood simulations, and in a wide variety of other applications.