I'm looking at an old boat - say's the bottom is coated with R-17. What the hell is this??

years ago when we first started hitting manatees (at a high rate of speed)we would coat our hulls with r 15,it would keep the blood from spraying in our eyes,i can only assume that r-17 is a gooder product(and yes, i am very aware that i'm going to hell)

i've always been a big fan of r-18 - jeff