But when you are talking about a public pool or something like that, the wants of the few people who feel like tossing a ball around don't outweigh the wants of the majority. THAT is the definition of selfish...when one person wants to do what he wants and does not consider others.
I routinely swim laps in our neighborhood pool. It is a junior Olympic sized pool with lap lines. I stick to one lane on the very edge of the pool. It is rude and selfish when I am there first, swimming laps, and people show up, jump into the pool in my lane and start tossing a ball around, right where I am swimming. They have the whole rest of the pool, but no, they need to encroach on my one lane at the very edge. I cannot tell you how often this happens and it is, by definition, selfish. Or when the pool is quite full, yet people show up with GIANT inflatables and then proceed to bump into everyone with them as they float around. FWIW, both these things are activities prohibited by our community and posted on large signs in the pool area. People breaking rules knowingly and encroaching on other's personal space is rude and selfish and there is no way to spin that the other way, sorry.