Water pumping?

[Rooster]

Just walked around the marina in Sarasota, FL. Many of the mobo's clearly with no one on board for a while have water pumping from the side, like when my bilge pump was working. Guessing not the bilge as lots doing it. What is it? Maybe air con?

 

[CaptainMike1970]

Highly likely to be the reverse cycle air conditioning running to keep the boat nice and cool for when they get back. We had it fitted to our last boat, very good but you couldn't leave it running all night or the sound of the running water leads to a "very interrupted" nights sleep!