I am always looking for new toys Here is one I found - which in theory would be awesome to set up to view the prop to check the condition of the zinc and if it is fouled etc...
Quote (Airmar product btw):
The CA500 thru-hull color video camera will display what is directly under the boat, making it ideal for viewing fish activity or as an underwater surveillance and safety system. The single cable output connects to any display with a PAL or NTSC (US standard) input. This version has a plastic housing (note image shows stainless version). Product Features
Camera 1/3" Sony CCD
NTSC 500 H x 582 V, 625 lines, 50 field per second
PAL 510 H x 492 V, 525 lines, 60 field per second
Minimum illumination 0.5 Lux day, 0.01 Night
Angle of view in water 92 degrees diagonal
Focal length 3.6mm (0.14")
Cable length 20M
The sapphire viewing window resists scratching or cracking. The unit is retractable for easy cleaning, and the housing has a self-closing valve to minimize water intrusion. A blank insert is provided."