Let’s face it: once in a while, you’ll see a dead fish “floating” on your pond. If they “float”, then it would be very easy to “pick them off” the pond.
But take note that not all of them “float up”; others sink. This is so because of the condition of their “swim bladder”; when it is still intact and “filled”, then they will float.
But if their swim bladder is blown, they tend to lie on the bottom of the pond.
The swim bladder is the internal organ in fishes that causes them to “rise” or sink in the water. With their swim bladder, fishes may implement weight and volume adjustments, and so they “rise” or sink to the bottom of the pond.
Hence, be always on the lookout not just for “floating” dead fish but also for those that have “sunk”.