Years ago, when my inlaws were redoing their kitchen, and got their first dishwasher, this topic came up with them. He wanted to give it a try. She said absolutely not. They didn't do it. But it supposedly works. Use filets, but not a whole fish. Season as you would for poaching fish via any other method. Make sure the packets are completly sealed, and put them on the top rack. I googled cooking fish in the diswasher. A lot of stuff came up, including some videos on youtube. Frankly, though, I think it's a gimmick, and maybe can be used for "shock value" if you want to be one up on a food snob. If you try it, let us know how it turns out.