It is fun to make a toy vehicle with Lego, but it is even more fun to make one that actually works. [PeterSripol] made two Lego submarines, and you can see them in the video below. There isn’t a lot of build information, but watching the subs fire missiles and then getting destroyed by depth charges is worth something.

One of the subs is larger and uses a rudder to steer. It was apparently harder to control than the other smaller sub which used two motors thrusting opposite one another to steer. Looks like fun.

[Peter] found that he had to use lower frequency RC controllers to penetrate the water. The smaller one seems to be trailing a wire, so we think it may not have even used radio control. There were a number of custom 3D printed parts that help motors and other electromechanical devices.

There were a few things we were wondering about, though. The electronics used are pretty conventional, and soaking them in water is probably not great for their lifespan. It wasn’t clear to us also, whether the submarines had any buoyancy control. We think air trapped inside just kept them sort-of floating until the air escaped.

Our favorite model sub is also our favorite starship. If you want an example of buoyancy control, look at this past Hackaday prize entry.