In a salt water environment, I would have my doubts about the reliability of that residential water alarm.
The Blue Seas 1842 is a very sophisticated (expensive) option. It does require a hole to mount and is a tad big but it can be mounted in spots other than the helm, like aft or in the cabin. It has the capability of powering a remote LED and/or a remote audible sounder. The nice thing about this system is that it keeps a running count of how much time the pumps were working. This model can monitor 4 pumps.
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