Overview
Lots of people seem to ask “Why does my ship not float?” and here is the answer.
Buoyancy
In order for something to float in Stormworks it has to have an enclosed volume of air.
(This is an engine limitation, that will very probably never change.)
(EDIT: Now there is sort of a workaround for this. See Open Boats section)
Lets say we build a boat shaped like a shoebox but without a lid.
In other words our ship has a bottom and four walls but no ‘ceiling’:
This box does NOT float (although it does, but that is only due to the bouyancy of the blocks themselves. Add a little weight and it will sink).
To the game there is a big hole in our shoebox, namely where the ‘ceiling’ (or shoebox lid) should be. So the air inside is not completely enclosed and our ship will not float, no matter how many pumps we install.
If we put the lid on the shoebox it will float, no pumps needed:
You can even access that enclosed space by installing a door- or hatch-block, but make sure to put it above the waterline. Otherwise you risk flooding the enclosed space when you open it.
If that happens pumps can be used to drain the water. Of course they can be used for flooding as well.
Open Boats
Now we can build open boats (sort of), by lining any opening in the hull with Door Frame Blocks.
Think back to the shoebox. Now, instead of putting a lid on it, we simply replace the top layer of blocks with Door Frame Blocks. Make sure they are aligned properly (all blue markings on the same side, arrows pointing inward). No Door Panel needed:
The game now considers the empty space inside the top layer to be part of the hull, thusly we get an enclosed volume of air.
Also, we HAVE to make sure, that the open door frame does not come into contact with the surface of the water. If we build our shoebox too small, with not enough bouyancy, it will immediatly sink after spawning and dropping down, because water floods through the door frame. There is a visible difference though, between a non-bouyant object hitting the water and a bouyant one, that floods due to being dropped.
Water will now flow in AND OUT of any watertight door.