Well, I was attempting to channel a cavern lake into the magma sea to surround a super-fun ore vein I happened to find there so I could mine it out. This scheme encountered several problems:
- First attempt: Channel a single hole over the sea. Result: Hole immediately plugs with obsidian, nothing else happens.
- Second attempt: Accidentally mistake "7/7 water" for "the tile above 7/7 water" and immediately dig into it. Result: flooding of my stairwell. Fortunately I had the foresight to have the stairwell a decent distance from the fort proper, so I was able to construct a wall before anything flooded.
- Still during the second attempt: Discovered that you don't actually need an up staircase on a given level to allow water to flow up from that level due to pressure. Result: second stairwell attempt, due to being dug entirely of up/down staircases, contacts a flooded area and starts taking on water as well.
- Third attempt: Channel out multiple bits of the floor above the magma sea, then flood the channeling chamber with water. Result: Water occasionally spreads diagonally, leading to obsidian being generated and immediately caving in. This messes up the whole casting process by flinging magma up to the level above, creating obsidian plugs that prevented the tile below them being properly solidified. This then cost me several pieces of super happy fun time ore thanks to them still being adjacent to magma.
- Still during the third attempt: The miner that poked a hole in the caverns decided that the best way to flee the ensuing flood was UP THE STAIRS, INTO THE CAVERN LAKE. He immediately began drowning, but miraculously stopped when enough water was drained from the lake. He even managed to make it ashore!
An unrelated mishap occurred when I was trying to build a magma pump for one of the sea's pipes: magma crab shot the worker, who instead of fleeing decided to stand there and get pelted. When he finally dodged one? Boom, straight into the magma.