Is it possible to cook a whole fish in a dishwasher?
Surely the authors of the previous (sublime!) answers will throw the "Sure it works in practice, but does it work in theory!?" at me, but this great SE question and its answers still lured me into creating an answer backed up by empirical evidence.

The Answer

YES! It's certainly possible. At least one successful attempt has been logged (see below).



The Experiment

The following equipment and ingredients were used in this experiment:


Two whole trouts (each 230 grams, 28 cm long, thickness 3 cm).
One salmon steak, cut in two equal pieces (90 grams each, thickest point 3 cm).
Herbs: rosemary and parsley.
Lemon slices (only on the trout, not on the salmon).
Sea salt.
Zip-lock bags.
Microwave foil (only on the salmon).
Dishwasher type: Bosch SGS55 (only sold in EU, it seems)




STEP 1 - Preparation

Salmon


Wrap tightly in microwave foil with salt, rosemary, parsley.
Put in zip-lock bag.
Push air out of bag, close it.


Trout


Salt, rosemary, parsley and lemon slices inside the fish.
Alas: the zip-lock bags were too small, I had to cut off the head and tail.
Put in zip-lock bag.
Push air out of bag, close it.




STEP 2 - Enter the Dishwasher


Rolled up the zip-lock bags a bit.
Put one salmon and one trout bag in the top rack, the other two in the bottom rack (to test the difference).




STEP 3 - Program

Here's the tricky bit. I read up on sous-vide before trying, noting fish (particularly salmon) would need around 50° Celsius at a constant temperature. However, my main concern was that the temperature would not be constant enough to cook the fish: I was more afraid of under cooking than of overcooking. So I decided to run my experiment at this program:


The highest program marked 70° Celsius
Run for the full 137 minutes
No detergent
No other equipment (plates, cutlery, etc)




THE WAIT

With the dishwasher empty, the first bit of the program made an awful lot of noise, with cold water hitting the inside of the empty dishwasher. After that it kind-of returned to normal.

STEP 4 - Results

After 136 minutes I was standing in front of the dishwasher eager like a little kid waiting to open his Christmas presents. The dishwasher felt really warm, even on the outside. When I opened the dishwasher I saw one of the bottom salmon bags had fallen to the bottom. This is what the bags looked like when I got 'em out:



Then, with hands shaking, I opened the bags. This is the result:



Victory! upon closer inspection it turned out the fish were all perfectly cooked! We put some extra salt on and enjoyed them very much.

Conclusion

The answer is then a wholehearted "Yes: this is possible!". Try this at home!