The uninitiated may ask whats the difference between waterbed sheets and sheets for a normal bed? Well water beds are a little bit special. The main difference is that waterbed sheets have a tendency to slip off the bladder mainly because of the vinyl layer but also because of the size of the water bed bladder or more accurately the depth of the bladder. Normal bed sheets aren't usually the correct size to allow for bladder depth and are also difficult to tuck under the mattress as it is water filled. As a result sheets are often ill fitting and likely to slide off the bladder. You could attempt to alter existing bed sheets or buy larger sheets to overcome the problems but more often than not the best solution is simply to buy special waterbed sheets.
Now don't be put off, although waterbed sheets are special in design they are not often special in price. When you look at waterbed sheets closely you will note that generally there are a few different options open to you.
If your waterbed is a soft side bladder type you should be able to find either elasticated sheets or fitted sheets, or sheets with elastic corner straps or pockets. Either type should be fine for use on a soft side. Take careful note of your bladder depth before buying.
Elasticated or fitted sheets simply have an elasticated edge that fits around or under the mattress keeping the sheets firmly in place. Corner pocketed sheets are as the name suggests, sheets with corner flaps for tucking under the mattress to keep the sheet in place. A variant of this design is the elasticated corner strap sheet. At each corer the sheet has an elastic strap attached across the corner, the strap slides under he mattress to keep the sheet in place. In all cases get sheets that will fit the mattress dimensions including depth of mattress. Obviously the elasticated options will give the most room for error.
Hard side waterbeds where the mattress sits within a frame offer a slightly different challenge mainly because of the lack of access around the frame. Generally you have a couple of choices. You can go for pole sheets, these are sheets with a sleeve along the edges that allow for a pole like a broom handle to be slid down them. The sheets are then fitted by pushing a poled edge down between frame and mattress on either side of the bed. So long as you have the right size the poles will keep the sheets nicely in place. Alternately you can go for the corner pocketed or elastic strapped sheets as described for a softsided waterbed.
Obviously getting the size of your sheets is important, with the correct size you can choose whichever format of sheet will best suit your bed. You'll find that the format of the sheet won't be the deciding factor on price but as with normal bed sheets the deciding factors are size (obviously thats a given) and fabric. When it comes to fabric your positively spoilt for choice, many stores sell a selection of cotton/poly mix, pure cotton, satin, silk, or even bamboo. The cotton/poly mixes are the most hard wearing and generally the cheapest, the silk and bamboo are the most expensive and luxurious. When choosing cotton bear in mind the price will be affected by the thread count of the cotton, the higher the more expensive but also the softer the touch. Also bear in mind buying full sets, which include sheets and pillowcases, is often the best way to get discount waterbed sheets.