Yup, got 600+ hours invested in From the Depths.
Been with the games development since august of last year, and it was initially released on steam early access back in january 2014 (I think?)
As I'm sure you've gathered, it's basically like minecraft, but instead of the planet being made of blocks, all the vehicles are. You can create anything from submarines to sailboats to spaceships, armed with anything from custom cannons, to missiles, and even lasers Defend your creations with various active defense things like shields, smoke, and a variety of other bits and bobs like flares, massive drills and harpoon guns :D. (bit more of a learning curve, but thats not saying much haha)
It's often described as a voxel-based RTS (your faction vs the world). But there's more to it than that.
From the Depths has several game modes though
Campaign - This world (the planet "Neter") has 8 factions controlling it, and you've gotta conquer all of them. All of the factions, their vehicles, and their lore (beyond a general outline provided by Nick Smart, the developer) have been created by From The Depths online community.
Creative - Infinite resources, can spawn in an infinite amount of enemies, can build whatever you want (and can save these blueprints to load in during a campaign, upload to steam and share, or easily post on the official forums)
Story Missions - Basically levels in the traditional sense, for example, one of the first missions is simply breaking through a certain factions trade blockade, you're given X amount f resources to complete the objective in any way you see it (and can afford)
Multiplayer- least developed part of the game so far, it can be quite laggy at times, but Nick's hammering out some optimization stuff for the game in general currently (cannon projectile optimization, and some other neat things like GUI simplification), and there will be a fully functioning MP experience in the future.
On top of that, there's now a new "Custom Campaign" option, where you can do anything from literally building your own planet, along with weather, atmosphere height, ocean depth, gravity, custom factions, lore, and vehicles. Additionally you can create your own story missions, and a whole slew of other things (Nick's mentioned that if any player created campaigns become "mature enough" he might ship them with the "default campaign" when the game is fully released)
As mentioned before, there's a very active and welcoming community on the games official forums. We're always glad to help out new players, as the learning curve can be a bit of a hump for some.
But fear not! Nicks currently working on a new GUI and the community is putting together some literal "walk-through" maps, to help new players learn about all the different types of blocks and how they fit together)