Assuming you have an existing wifi or ethernet connection to the vessel: It is pretty trivial to convert the output from existing float switches and other water level devices (you don't tell us what you have) to a GPIO pin. A python or bash script can handle the email message. This is not tuff and there exists lots of examples on-line.
Nothing replaces double clamping on all hoses that go to through-hull connections below the water line and regular visual inspection. Further, ball valves at the through-hull (before the double clamps) being closed whenever the vessel is unattended allows much better sleep. You may need a check list, before and after, for every time the vessel is used. The through-hulls need to be inspected and replaced as needed (annual inspection usually adequate) because even bronze is subject to electrolysis and I won't even go into plastics.
To rely on devices to warn you when the vessel may be going aglub is too little, too late.