A float (not to be confused with a drifter) is an oceanographic instrument platform used for making subsurface measurements in the ocean without the need for a ship, propeller, or a person operating it.
Once a certain amount of time has passed, most floats will rise back to the surface by increasing its buoyancy so it can transmit the data it collected to a satellite.
Floating devices with neutral buoyancy were developed independently and simultaneously[3] by Henry Stommel in 1955[4] and John C. Swallow in 1955.
A common sensor used is a CTD to collect data about the conductivity, temperature, and depth (which is related to pressure).
These floats are capable of making a few hundred profiles to a maximum depth of 2000 meters before battery exhaustion, and transmit their data to shore via satellite communication each time they surface.
A major user of profiling floats is the Argo program, which aims to keep 3000 of them functioning in the ocean at any given time.
[clarification needed] These floats drift at a set depth for a period of 5 to 10 days before surfacing to transmit the data to satellites.
A newer model for a coastal float is being developed by the Monterey Bay Aquarium Research Institute (MBARI).