Well, you see. When a merman and a mermaid love each other a LOT, they decide to have little fish-kids... so the Magic-Water-Stork comes to drop a Magic Shell that contains a little egg that turns into a merman or mermaid within five months.
Real fishies make babehs by like, the girlie lays her little egglings and puts them in her mouth and the boy fishie swims in front of her and wiggles his little tail and BAM. I like to call it a no-contact blowjob. XD