A YouTuber has managed to make a working LEGO submarine work using Power Functions, without it getting flooded, using magnets.
There are many great things that LEGO fans can motorise with Power Functions, but submarines and even boats are a challenge. Stopping them from letting in water, which will of course cause problems for the components and batteries, is a barrier for most builders.
In this video from Brick Experiment Channel, a demonstration shows how magnets and a container have been used to make a working, controllable submarine that won’t flood. An IKEA food container holds together with magnet couplings, allowing minifigure to take the submarine around a swimming pool.
Propellers on the sides, controlled from motors on the inside, drive the sub up and down.
It’s one of those projects that is easier to admire than replicate, but with lockdown lite still keeping many people at home, perhaps all of that free time will encourage LEGO fans to try out these trickier contraptions.