I haven't tried it Bike, but read about it in the cooking section of the paper. It's supposedely makes great tasting fish!
First, it is necessary to state that the dishwasher must be clean, and no dishwasher detergent is used during this off-beat cooking procedure.
The cooking process in use is just simple poaching. This requires sustained heat levels of around 140 degrees F. for approximately 15 minutes per pound of fish to be cooked. The fish should be in a virtually air-tight pouch of aluminum foil -- one of those clear plastic cooking bags, sealed with duct tape, would be a good thing to put over the foil-pouched fish. If the fish is to be "stuffed" with things like onions or other vegatables, they should be sauteed in a hot pan first, since they won't cook well in the pouch. The dishwasher will produce enough heat to cook the fish, but not anything inside, so this method would work better with fairly thin fillets, rather than whole fish.
You should first ensure that your dishwasher's heater element is working well enough to get the water temperature up to 160 deg. F.
BTW, I've never tried this myself, and even though it would work, absolutely would not recommend it. It's just as easy to poach fish in a pan of water on the stove. The reason I can think of doing it this way would be if you had a malfunctioning stove but a properly functional dishwasher. Even then, I think I'd build a campfire in the backyard before trying anything like this!