Exactly. Flies look much the same in water as in the air - as long as they are not moving. Once you swing them in a current or retrieve them, they slim down (and wiggle).
Another thing a lot of people forget is that food items (insects, small fish) look glossy when you take them out of the water but in the water they are matt. Of course, the flash from a varnished or epoxied artificial may attract a predator's attention so they still work. I just wonder whether those old dubbed fur patterns work because they are matt and look more natural underwater.