From the Depths Showcase: Dory Submarine
1Being a glass cannon doesn't matter if nobody can hit you.
The goal here was a submarine I could deploy almost immediately in a campaign, very cheap, but also offensively capable (at least against ships) and hard to hit. Except for metal around the ammo, it's all stone and essentially unprotected. One torpedo hit would end it, but it goes 30 m/s and has torpedo defenses. Torpedoes or a very fast ship with advanced cannons and supercavitation are almost the only things in the early campaign anyway that could hit it.
In keeping with what is always my policy with submarines, there are no wireless receivers on it: everything is connected with AI connectors. Therefore it cannot be detected with wireless snoopers. The only detectors are passive sonar and a wireless snooper.
For fuel economy and compactness, I went with fuel engines. Depth is controlled by hydrofoils and secondarily with an air pump, both controlled by ACB's. It is designed to stay around 70-76 meters depth. It has 2 propellers controlling pitch, 2 propellers controlling roll, and 6 propellers controlling yaw. It has a couple repair bots, not that they are going to help much with anything more than light damage.
It has one missile for anti-air and five torpedoes for anti-ship. Anti-torpedo defense is managed with one missile launcher launching a harpoon loaded with regulators and sonar target simulators every 15 seconds. The sonar target simulators are designed to wait 1 second before they turn on, hopefully to avoid attracting torpedoes towards the boat.
And essentially that is all there is to it.
In other news, I am still intending to build some more sugar rockets but haven't found the time at present.