 a waterbed, water mattress, or flotation mattress is a bed or mattress filled with water. waterbeds intended for medical therapies appear in various reports through the 19th century. the modern version, invented in san francisco and patented in 1971, became an extremely popular consumer item in the united states through the 1980s. ==construction== thumb|softside waterbed 160 Ã 200 cm with dual heating waterbeds primarily consist of two types, hard-sided beds and soft-sided beds. a hard-sided waterbed consists of a water-containing mattress inside a rectangular frame of wood resting on a plywood deck that sits on a platform. a soft-sided waterbed consists of a water-containing mattress inside of a rectangular frame of sturdy foam, zippered inside a fabric casing, which sits on a platform. it looks like a conventional bed and is designed to fit existing bedroom furniture. the platform usually looks like a conventional foundation or box spring, and sits atop a reinforced metal frame. early waterbed mattresses, and many inexpensive modern mattresses, have a single water chamber. when the water mass in these "free flow" mattresses is disturbed, significant wave action can be felt, and they need time to stabilize after a disturbance. later types employed wave-reducing methods, including fiber batting and interconnected water chambers. more expensive "waveless" modern waterbeds have a mixture of air and water chambers, usually interconnected. thumb|softside waterbed 160 Ã 200 cm with two waterchambers and flexible chamberisolation inside water beds are normally heated. temperature is controlled via a thermostat and set to personal preference, but is most commonly average skin temperature, 30&nbsp;Â°c or about 86&nbsp;Â°f. a typical heating pad consumes 150â400 watts of power. depending on insulation, bedding, temperature, use, and other factors, electricity usage may vary significantly. waterbeds are usually constructed from soft polyvinyl chloride (pvc) or similar material. they can be repaired with nearly any vinyl repair kit. ==history in 1800s== a form of waterbed was invented in the early 19th century by the scottish physician neil arnott. dr arnott's hydrostatic bed was devised to prevent bedsores in invalids, and comprised a bath of water with a covering of rubber-impregnated canvas, on which lighter bedding was placed. arnott did not patent it, permitting anyone to construct a bed to this design.an encyclopaedia of domestic economy , webster & parkes, harper & brothers, ny, 1855 google booksdr. arnott's hydrostatic bed, [[lon
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