I have a couple of wireless, battery powered, cameras on the mooring which link to my phone via WiFi. At any time I can open the app and view the camera(s). Those would do for your boat. No wires or issue of where to plug it in. USB rechargeable. You can use them as view only (ie: it doesn't record anything) or you can record to a storage card and/or send the footage to the cloud. for extra security. Using the app you can turn on/off the light that's on the front of the camera and even use it as a walkie-talkie of sorts.
https://www.amazon.co.uk/gp/product/B08HHVRM32/
£40