When will Minecraft add an update that makes it so if you place a fence underwater, it doesn't create an air pocket around it? It can be frustrating when trying to build an underwater structure, and there is random blocks of air all over the place.
The blocks that can be waterlogged (fences, trapdoors, walls, stairs, slabs, glass panes, and I assume iron bars) will automatically waterlog when you place them into a source block. They will also automatically waterlog if you placed 2 sources adjacent to them in such a way that they form a source block in that block's location (the creation of an infinite spring).
These blocks will NOT automatically waterlog if you placed them on dry ground and then splashed water around them, but you can manually waterlog them by rightclicking a bucket of water on them.
All of this works in both directions, too. If you placed a block in water and then removed the surrounding source blocks, the waterlogged block would remain waterlogged. Clicking with an empty bucket will take out the water.