Here we have a sink drain hose that is barely connected to the drain pipe on the sink. If the hose were to fall off, or get knocked off, the boat could sink.
There seems to be a problem with many “Marelon” plastic type seacock valves being stuck in the (usually) open position. This may be the result of Zebra mussels in the valves. Like all seacock valves these need to be opened and closed several times a year to prevent seizure.