Abstract: Rudimentary prior art fluid-inflatable sleeping mattresses are of a simple six-sided shell construction having a spout for fluid introduction and evacuation. Disclosed are improved mattress constructions which, in addition to the prior art spouted six-sided shell, are internally provided with substantially parallel fluid-impervious baffle-panels resulting in solely terminally communicating internal chambers for the external shell and that drastically reduce abrupt fluid displacement phenomena as the reclining occupant moves about. For water-inflatable modes, one or more air-relief valves extend from internal chambers through the external shell to facilitate purging of air bubbles entrapped within the water flotation medium. An air-impervious cap for the spout means permits an internally baffled shell to be alternatively employed as an air-inflatable type flotation mattress.