I've embarked near an ocean, and I figure what's a good use for a ton of water? Drowning traps of course. But as I was in the process of setting it up, I noticed something very odd. I will try to explain as best I can, english is not my native language.
http://img713.imageshack.us/img713/8876/trap.pngWhat you see is a dug-out layout for a trap gauntlet. The lower part will be a drowning trap, and the part above will be falling traps. You should be able to make out the 3tile wide path snaking through (entrance not yet dug).
The Z-level below contains a dug-out water river leading to a reservoir (which I intended to pump from), which has channeled access to water in the picture. I've marked it with a red rectangle. The river is constantly connected to the ocean.
Now here's the odd part. When a wave arrives on the beach, the markers for where the wave splashes, signified by my red arrow in the picture, bugs out. Instead of splashing somewhere where it ought to, it travels through the walls, riding on the river below, until it reaches the end of the river. But the two z-levels are not connected in any way. Thus, my completely enclosed trap layout receives magical splashes of water from waves in an underground river. The area is completely roofed over. (just to be clear, the channeled tiles in the top of the picture are not connected to the water reservoir/river)
So, how do I stop the magical waves from wallhaxing?