Personally, I'd pump out water near the opening and build a floodgate/bridge/wall real quick to seal it off. I would recommend a wall for now as a temporary, easy to construct measure. Then drain it from another side by either channeling it into an aquifier, into the caverns (it'll flood off the map/evaporate), or into an end-of-map drain (tunnel to map edge then smooth/carve fortification on the last tile to let water flow away). I suppose if you had a good drain you could open that up first while pumping water back into the ocean to make the construction easier. Pumps can easily remove water from a tile faster than they enter it, but you will likely deal with several cancellation messages (just pause and un-suspend until it is completed, progress isn't lost). Once the water is gone, you can retrieve BOTH bodies and their items. You want to entomb those dorfs (or at least carve a memorial) to prevent ghost attacks. Once recovered, you can build the reservoir the RIGHT way and fill it again. I recommend later replacing that wall with a raised bridge (floodgates can be destroyed, raised bridges cannot). Once drained, you reseal the reservoir and fill it again. There really is no such thing as "permanently drained" when we can endlessly make walls, floors, lever-controlled hatches and drains, etc.
Look, no reservoir is built right unless you can both refill it and drain it again on command for exactly the problem you are having. If someone falls into the reservoir, you need to be able to empty it on command and recover the dorf before he drowns. Typically you'll want a lever controlled drain (either floodgate, bridge, or hatch) and a lever controlled way of filling it up (Gears can be attached to pumps to turn them on/off). I suppose you could just dorf power the reservoir full at the beginning, though. Since this is an ocean you WILL have to pump it at least once anyway (to remove the salt). Also make sure the reservoir is at least 2 z-levels deep. Even after being pumped, 1-tile deep water will always contain a "dusting of mud" that is created when the water hits any dirt, stone, or constructed floor. Your reservoir could technically be 1 z-level, but then you drain it (via lever) into a narrow (but deep) secondary reservoir that you dip your well into. The second concern for a well-built reservoir is safety. Building destroyers or amphibious pests shouldn't be able to swim through it and get to your fort. This is why I (again) recommend gating it off with raised bridges. Grates and fortifications can be swum through when flooded.
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Topic: Ocean pumping disaster - I want to recover items (Read 548 times)