I was sitting by the aquarium at my Doctor's office watching the fish. How do fish mate?

[eppur_se_muova]

5. There are variations, of course. Like mouth-breeders and pouch-breeders (seahorses).

And then there's the cast-it-all-into-the-sea approach, where tight gatherings of males and females dump all their gametes in the water at once, not much different from pine trees. There are times and places along the seacoast where the waves are frothy with fish spooge after such spawnings, usually timed to the phases of the moon.

Different environments, different adaptations, different "strategies".