I lived in a seaside village in Korea. Sometimes I'd stay up all night and go down to the low cliffs to watch the sun rise.
Once, just as I was starting to head home, I heard a far-off splash and turned to look. I thought it was fish, but then I realized it was dolphins. They were splashing around kind of randomly.
Within seconds, the dolphins arranged themselves in rows and started swimming in my direction.
Then they paraded past, right in front of me. There were about 50 of them. I marveled at the perfect semicircles their bodies made each time they rose out of the water.
When they'd all gone past, they turned and swam out to deeper water again.
I mentioned this to a local, and he said, "No, you don't see groups of dolphins around here. You might see one or two."