I think that to describe it as sous vide cooking is wrong, as the revelation in commercial kitchens is slow water baths which hold the temperature exactly what you require for exactly how long you like, there for providing the perfect slow cooker - as for sous vide, thats just there to keep all the juices and flavours in and to ensure that it cooks evenly by removing any air. Boil in the bag its not as it should never boil - defeats the object. as for just set fish, its absouloutly superb, when you take any fish over 40 degrees it brings out the proteins in the flesh and changes the texture, if cooked at 40 degrees you still achive the 'translucent' stage and poached fish to perfection.