The last time an article about this was posted (many moons or so ago), seems like all the feet found were either all left or all right feet, can’t remember which. I don’t think the surf would be so discriminating. And Always just a foot, never a skull, and arm or a hip, just a foot.
Feet are often protected by shoes and hold together much better. Nothing about other body parts would cause them to float, aside from intact bodies.
As for rights or lefts being more prevalent, the sample size is very small. Get up to 10 or more and there is a statistically relevant trend.