Just like inner stretch fabric spring beds and memory foam

 beds waterbeds come in a range of sizes. To ensure your waterbed sheets fit on your bed you need to make sure you know the size of your waterbed. Almost as important as the size of your bed is the depth of your mattress. These are the two important size elements you will need to know to get properly fitting sheets. There are a couple of different types of frames for waterbeds. The type of frame you have on your bed will affect the kind of waterbed sheets you want to buy. The two basic types are soft frame and hard frame. If you have a hard frame bed you may want to look for pole sheets, which will make keeping your sheets on the bed a little easier. 
As with regular beds, waterbeds come in King, Queen, double and twin size. The waterbed also comes in a super single. This is a little larger than the twin, but not as big as the double.
Most waterbeds are longer than regular beds, measuring in at 84 inches instead of the standard bed size of 74 inches. This means it will be difficult if not impossible to use regular bed sheets on your waterbed. You will need to get sheets made specifically for waterbeds, because not only are they the right size, they have unique design features that help keep the sheets on the bed. 
When shopping for waterbed sheets you have a couple different choices. You have the regular sheets, and pole sheets. Waterbed pole sheets are great for keeping the sheet in place. In fact, people use them because they don't come off until you take them off. Pole sheets are constructed with a casing in each of the corner pockets of the bottom sheet. When you make the bed you slip the pole through the casing. It will grab the corner of the wood frame to hold the sheet in place. It stays in place until you are ready to take the sheets off of the waterbed mattress.
You can also find sheets for any size waterbed mattress.  No matter what size waterbed you have you will find waterbed sheet sets that are connected at the bottom in the middle. Being attached helps keep the sheets from sliding off the bed, and helps keep them together on the bed.
No matter what size of waterbed you have you will be able to find waterbed sheets and waterbed sheet sets in a wide variety of colors and fabrics.  You will also be able to find sheets that stay on your bed, at least until you decide to take them off.