A floatation device with a buoyancy chamber and cryogen reservoir

A floatation device 100 is provided comprising a buoyancy chamber (110, Fig 1); a cryogen reservoir (210, Fig 2A); and a heating pipe (310, Fig 3A) providing switchable fluid communication between the cryogen reservoir and the buoyancy chamber. The buoyancy chamber, cryogen reservoir and heating pipe may at least partially be contained within a housing 112. A method of raising an item from the seabed is also provided. The method comprises the steps of lowering a floatation device to the seabed; attaching the floatation device to the item to be raised; creating a supercritical fluid within a portion of the floatation device; and allowing the floatation device and the item to rise to the surface using the buoyancy of the supercritical fluid to raise the item to the surface.