[km0120]

>I know it has something to do with the anime School Days.

Yes, "Nice boat." is the byword for the anime School Days.

The last episode of "Scool Days" went off the air.
The sensational murder case happened in September, 2007 that a daughter had killed her father in Kyoto, Japan.
Because the content of the episode was that characters were cruelly killed, broadcast stations concerned that viewers might find it imprudent.
They devoted the airtime of "School Days" to that of landscapes in Norway: mountains, castles, fiords.
While Japanese anime fans were very disturbed, a foreign anime fan left a message, "Nice boat." to see a screen capture uploaded.
The cool and brief message made them laugh loudly.
The phrase became popular among them soon.