This is the most popular oxygenating plant for the typical garden pond. If planting a very large pond I would go for a British native instead. I have grown it 1.2 m/4 feet deep and have heard of it growing to depths of1.8m/6feet. Minimum depth suggested would be 30cm/12 inches. As with all oxygenating plants it needs thinning out once or twice in the Summer when nicely established.
Price varies on how it is sold. Sold in bunches or pots ready to put on the bottom of fthe pond. You can just throw in bunches which generally works but pots always seem to establish.