AQUATRON, A WORLD SUBMERGED
In the Oceanus System, the planet Aquatron is a Class A, compatible with most carbon-based life… if, of course, they're perfectly okay with water. Because there is a LOOOOOOOOOT on Aquatron. So much so that at least 90% of the surface of the planet is submerged under it. As such, the vast majority of the local lifeforms are, of course, aquatic, and this extends even to the local Cybertronian population.
Like many colonies, Aquatronian civilization began as a Energon Seeding and Mining operation, but over the ages, Aquatronian energon had been refined in an interesting way involving Oxygenization, making it cheap to produce and extremely efficient. As such, the society that had exported this energon soon grew rich from the profits of their trade, and so dolled up their humble little world to create a society of equality and peace, the very center of their world's society the capital of Wednestria, ruled in the loosest sense by a Leviacon named Poseidron. Despite this, there are always some problems, usually involving pirates.
In recent years, however, Aquatron has become home to a small regiment of the Military Defense Corp, who mostly use similar aquatic modes to the native, although definitely more mechanical than animal. The reason why isn't really something they're okay disclosing, which raises some eyebrows...