Not about Speedos, but short shorts.

[Minimalist75]

If my memory serves me correctly, volleyball shorts were extremely short in the era of short shorts for sports in general and got long more gradually than in other sports, notably basketball and soccer.
In beach volleyball most men wear long board shorts but shorter shorts and even speedos are allowed and seen occasionally. I know a beach volleyball player who knows someone who always competes in speedos and he thinks that gives him an advantage.