A flotation mattress is provided in which the downwardly directed weight of the user's body on the top wall of the mattress is counter-balanced substantially only by a force directed vertically upward by the buoyancy force of the liquid in the mattress, and not by any substantial tension or tautness in the top wall of the mattress. The top wall of the mattress is of sufficient surface area to conform to and envelop a user while still keeping him or her dry. A liquid which is more dense than water, such as salt water may be used in the mattress. The liquid in the mattress, in conjunction with the excess top wall material which yields substantially completely beneath the user's body, strongly simulates flotation in a liquid. The amount of excess top wall material will be selected in such a manner that when the mattress is filled with the proper amount of liquid and a user assumes a supine position on the top wall, the top wall will have both a sufficient length dimension and a sufficient width dimension to substantially completely yield beneath the users body without the top wall itself providing substantial support to the user. In one embodiment of the present invention, the confined liquid mattress is placed on a horizontal internal surface within an isolation enclosure constructed of light weight prefabricated panels, which enclosure provides a space in which a user may recline comfortably in a dry flotation environment.