John Crossley Swallow FRS[1] (11 October 1923 – 3 December 1994) was an English oceanographer[2] who invented the Swallow float (sometimes referred to as a neutral buoyancy float), a scientific drifting bottle based on the messages in bottles that shipwrecked sailors hoped would reach inhabited shores, summoning assistance.
He is the inventor of the "Swallow float", a hydrostatically stable, freely drifting source of sound underwater, which can be followed by a ship at the surface.
By numerous observations with this ingenious device, he and others have completely changed our picture of the deep circulation of the ocean, showing the presence of strong deep currents in the western North Atlantic, and a reverse flow beneath the Gulf Stream.
Swallow combines a devotion to his work and a careful attention to detail with a mastery of the practical handling of a research ship at sea.
[3] Swallow designed his float to reach neutral buoyancy at a desired mid-water depth.