Dock supplied, pressurized water is never a good idea in a boat.
It’s also possible although unlikely the pressure reducer failed.
When a pressure reducing valve fails, it is very often the result of the diaphragm rupturing and the valve goes wide open.
Dock supply pressure is now inside the boat's water tubing and can cause problems if the tubing can't withstand the uncontrolled dock water pressure.
It doesn't even have to be that dramatic. Let any tube fitting separate inside your boat and you've got an endless supply of water flowing into the boat. Now that's far worse than your hull hitting a sharp rock when your under way. At least under way, you're on the boat to staunch the flow of water.
However, back at the dock when you're boats all alone and nobody's home .....................
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