Why do ships always seem to be pouring water from the side?

Question

I always see ships that seem to be shooting water from the hull, why do they do this?

Is it water sucked in by the engine for cooling purposes which is then pumped back overboard?

https://i.redd.it/ip5h2hn9qq791.jpg

In: 4419

Answer 1

Fishing ships need a stream of new oxygen-rich water in their tanks so their catch doesn’t die. Gotta get rid of the old water too.
The one in the picture is a military ship though, so different reasons there.