Marine instruments used to measure ocean currents air temperature, water temperature, wind speed or salinity. A floating, anchored marker used as a navigational aid or to mark a danger spot.

Floating object used as a marker or automatic platform in the ocean and lakes. A buoy can drift or be moored, and can be deployed on ice. Sometimes fitted with sensors to make measurements. The Argos system serves over 2000 buoys, for meteorology, oceanography and glaciology.

Floats that warn of hazards such as rocks or shallow ground, to help ships maneuver through unfamiliar harbors.