Looking good, Bob.
I'd like to add a note about the propulsion motor.
For guys(or gals!) who would like to incorporate a motor similar to Bobs in their subs, a few points to mention.
Scrap yards (car breakers) are an excellent and very cheap source for motors. Here in the UK, surplus stores are few and far between, but breakers are very prevalent, and with old cars being disposed of at an ever increasing rate, there's rich pickings to be had for modellers who wish to break free from the "mabuchi" mould.
Modern cars are absolutely jammed with quality electric motors that would cost an arm and a leg in model shop (if you could buy them, there) and generally exhibit the following characteristics-
High torque low speed winding
Multi pole armature- i.e. 13 poles or more, fan motors often have upto 22 poles. How slow can you say "smooth low speed running!"
Wide can design for wide armature i.e. 2" to 3" diameter or greater. With the addition of low RPM, this means no gearbox required for all but the largest of models.
Wide voltage range- these motors can take voltages anywhere between 6-18 volts without any difficulty.
Low current draw.
These motors are generally built to last, so tend to be a little heavy.
Consequently they're generally only suitable for models of around 40" upwards.
That's about the only disadvantage.
No more than £2-5.
Places to look for the motors?
Electric radiator fan.
Electric heater (interior) fan
Electric window motors.
Windscreen wiper motors.
As an example I recently opened up an electric radiator fan motor, which came off an old Ford.
Inside, I found four heavy duty carbon brushes, a 22 pole armature approximately 3.5"diameter. Ballraced front bearing and bronze rear bearing. Cast aluminium can.
This motor will last for ever!
Would suit a boat of 50" or more.