”Leva” is to exist, to have life. ”Bo” is to have a place to live, like where you sleep and eat etc. You could say that fish ”bor” in the water but it sounds like they can live on land but they just happen to have an apartment in the water where they stay. ”Leva” is more to permanently exist.
so while a fish "lever" in water and a human "lever" on land, a human would "bor" in a house?
That is up for debate I believe. While I do say fish to mean multiple, some people do use fishes to differentiate better.