My family has raised me on the water. I truly mean this. I am pretty sure I knew how to swim before I could walk, and I learned how to drive a boat well before it was legal for me to attend drivers training. For us, boating and water was the way to live. I remember having college kids on my lake come ask me for tips on slalom skiing when I was in elementary school. (This may be an exaggeration. They might have been in high school only, I just remember being young and the people asking me being very tall.) My point however is, that my family is devoted to all things water or boat. So when it comes to linear bearings, we would have to choose the slide bearing because of its many uses in the marine industry.
Slide bearing are made up of a moving carriage and a stationary base and are used to glide items across a surface with low resistance to motion, usually through the use of a high performance polymer or a self lubricating material. They are often used instead of ball bearing systems. In the marine industry, this is beneficial because the ball bearings could corrode more easily, or move when they are not supposed to when exposed to flowing water. Often these products are made by two plates of low-friction materials being stuck between to metal backing plates. From here, these plates are attatched to a high strength bar made of a metal (for marine industries, a corrosion resistant one) that is able to bear the weight of the load. While I like to assume everything should be made for the water, these products are very useful on land as well. Some can even be made with covers or bellows to protect against dirt and other interfering particles. These products are also able to last longer than ball bearings in most cases, making them valuable to a number of industries.