Floating Bases

You can purchase in /s or craft them at a tier 2 work bench.

Expanding

Once you've deployed your first "starter" water foundation, all the subsequent foundations will be placed using vanilla building mechanics - just take a building plan and build some floors neighbouring your water foundation on the sides! If you have enough water foundation items of the required kind in your inventory, those newly placed floors will also turn into water foundations. And they can call be demolished/upgraded, just like normal twig structures, as soon as you place a Tool Cupboard. Expanding a single-sided water foundation requires 1 proper water foundation item, expanding a double sided water foundation (reinforced one) requires two.

Reinforcing

Reinforcing a water foundation means making it double sided - so it fully covers the soft side AND gives you the ability to build from the surface down, to the seabed/lakebed! To reinforce, make sure a built water foundation is fully repaired, and them hit it with a hammer. If you have a required water foundation item in your inventory, it will be consumed and the foundation will be reinforced: you will see another floor with floatation barrels attached upside down. If you try to expand a reinforced foundation (by attaching a floor at the bottom, reinforced side) and there's no water foundation above it (normal orientation), it will try to create one, provided you have enough items in your inventory. Reinforcements (upside down water foundations) are always associated with the water foundation they're attached to and cannot exist on their own - if you destroy the water foundation, its reinforcement will be destroyed too. However, destroying the reinforcement will not destroy is water foundation.

Upgrading

Upgrading Water base structures Building blocks inside your water bases have certain tier limits associated with them - it's to help balance things out. By default, non-VIP and non-admin players will be able to upgrade water foundations to sheet metal tier, floor frames and wall frames to stone tier, and everything else (including walls, floors and reinforcement foundations) to wood tier. You can easily decide which permission profile has which max tier (per type of building block) in the config.

Features

Water Base exclusive features

Because water foundations are treated as floors with the stability of a foundation, you can place roofs at "ground level", which is not possible with normal foundations!
Similarly, you can leave a "hole" where a water foundation would be and place a floor frame with a hatch instead - now you can enter your base from the bottom, underwater!
Reinforcing a water foundation means you'll be able to build down from the surface to the bottom of the water to create extra layers of protection, or...

Nettings deployed in wall frames underwater will collect random junk items