mmmmresin with crushed wallnut shells sound like 24 grit sandpaper to me !! 
I was just looking for diamond plate rubber flooring to line my toolbox drawers and make a top surface for the bottom cabnett, maybe something like that would work.  it seems it's a hassel to get though. it's black too and would get hot as hell in the summer...nevermind 
I can't think of many non-skid surfaces I'd want to sit on in a bathing suit.