The original stuff on my boat is a 3M product with stainless steel beads set in a grey- black compound that you trowel on at an 1/8 to a ľ thick directly onto the ply. This stuff is designed for use on public walkways so can take heavy use and poor environmental conditions.
I am mixed about its performance, from a grip point of view itís great, giving good non slip performance regardless of what shoes you wear
What is frustrating is that if you want to remove it you have to use a cup wire brush in a grinder because it sticks so well, While on the other hand I have one or two places where it has come off for no good reason
I think pete7 advice about cleanliness might be a contributing factor but 3M said not to worry too much.