I built shower grates about 20 years ago along with grates for the cockpit
sole from teak
. I had a wood shop at the time so I was able to do with from stock. The shower grate is 3/4 x 3/4 and the cockpit
is 1x1, neither have any finish. Two times a year for the cockpit and once a month for the shower I scrub them with something like soft scrub and an old teak cleaner brush and they look great, almost new.
I don't think hard finishes will hold up well because of all the edges and corners which breach soon and then undermine the finish. And the unfinished teak gives the best non skid finish. The pics were taken last year after 20 years of use and the above maintenance