Hybrid water lilies would be an obvious 'first choice' for a pond, creating shade from hot sun, food for many aquatic species.... and well, they are about as good looking as you can get on a pond...
Aquatic iris might be next to locate and plant, while they may seem slow growing, when they get to form large bold groups they form extensive root networks which provide great shelter for crustaceans and tiddlers, create shade in the hottest locations, great foliage through the year, in numbers they have a good reputation for improving water quality, quite easy to lift and create new positions, rather well behaved plants on just about every criterion...
Yellow flag iris tends to be a bit too large and invasive, that is just about the only badly behaved iris there is on a pond. Good ones might be considered to be louisiana, laevigata, virginica, sibirica
As they take a while to bulk up numbers, I'd be tempted to establish those early
Beneficial 'natives' like pickerel, Arrowhead. Arrow Arum and smaller forms of cattails (typha laxmanii, angustifolia) could follow those. The two big native cat tails should be kept well away from any lake, they tend to become unmanageable...
Regards, andy
