Was thinking of this:
"These are the boards we use for swim platforms and trim. The boards are solid and manufactured using a foaming agent that makes the center less dense than the outside "skin". This allows the boards to be screwed without pre-drilling. They have the smoothest texture and most eye-appealing color. By its' nature it is less slippery wet than dry. Standard colors are White Black, Gray, Teak, and Weathered Wood. A knurled surface can be applied for an additional 10 cents per foot. The knurled surface is a pattern of 1/16" squares pressed into the surface of the board."