usually smells a lot, and can be found floating in public toilets, because it's too large to be flushed. or in third world countries where toilets aren't available.
paranoid person#2: euw! flush it quickkkk!!
paranoid person#1: i can't its a yellow submarine!
bacteria: we all live in a yellow submarine, a yellow submarine, a yellow submarine!!
lil kid: daddy look at that yellow submarine in the river!!