Abstract: A bed sheet for water beds which is substantially rectangular in configuration and dimensioned to cover the top of the fluid-filled mattress. Integral extensions project from the four sides of the sheet and are adapted to be draped over the mattress and positioned between the mattress and the rigid walls of the bed frame. A hemmed pocket is stitched onto each extension and rigid rod means are insertable into said pockets so that, when operationally positioned, the mattress cooperates with the rigid walls of the bed frame to positively grip the rod means therebetween.