you could do that.they should grow well.try to stay around 3 ft.the lilies should grow better in 3 ft.of water

I think they would grow, too, but they could take over. You'll still have to divide them regularly or eventually you'll have a pond where the lily leaves will fold upward, be so dense that you can't see the flowers and, plus, you won't see any water surface.

In a deeper pond, lily tubs could be stood on blocks so they can be reached at arms length

The purpose of the lily tub is to anchor the waterlily, which when it is not rooted in is buoyant and likely to be a bit messy in growing habit if it is floating

Theres no need to store hardy waterlilies indoors, they are hardy outdoors in a pond, set below the likely freeze line

When waterlilies are growing in water too deep to wade, that is a problem, reaching them. You might try something like a boat hook to pull them to pieces where their roots are in soft mud...

If you can feel the plants with your feet, put on a face mask, hold your breath and have a fun time doing an underwater tug of war lifting stray rhisomes where they wander

Figuring a way to set a lily tub on a pedestal at a depth which is convenient to plant makes it easier to move the tub to a shallower depth to sort them out

Waterlilies have varying growing habit, some trot 6' in a Summer, others trot a few inches a year. Needless to say the very invasive fast spreading types tend to be cheap and easy to find and probably the most unsuitable to plant on a very large pond.

Marliac type waterlilies which have slow spreading but prolific blooming habit would better suit a position which is difficult to plant, that you do not want choked...

When I had my lilies in pors I used hanging pots that way they had a hook on the pot I could snag to retieve