I have done it but the fertilizations was problematic, so I got fewer flowers.

Root development can be good with bare root planting, no reason at all why it wouldn't get to a blooming size in a month given moderate water fertility and growing temperatures, quicker than a potted plant

Downside is the plant is vulnerable to aggressive grazing fish or turtles, the plant is not so well anchored and could be blown adrift in a storm, or float to the surface during risky Winter weather

Depends on what you want. We plant EVERYTHING in pots because it makes maintenance sooo much easier. Do you see the pot, yes, but most people are happy with the pot over trying to keep their lilies under control. Its uncommon, but given enough time lilies can get through liner and cause issues. Its more common with the cheap under 45mil liner, but it can happen. If you are doing your own maintenance I would suggest potting them and than trying to camo the pots.

I agree, pots are easier, plants bloom better. Lilies would become invasive and take over the pond trying to find soil. Because if they are bare root, that's what they will try to do, keep on searching for soil because that is how they grow in nature. And you can't fool Mother Nature, no matter how much you think you are God/Goddess of your pond. ;) An average pond does NOT have enough nutrients in the water for a bare root lily to thrive. It may survive, but it won't look happy.
You don't see lots of people posting pix of their bare root lilies blooming. And anyone who claims they grow better bare root should back up what they say with photos. Cuz it's just not factual. Lilies grow better in soil, and bloom a LOT better too.
Pots can be visible, but if you use black pots (or very dark colors) once the pads come to the surface and spread out, you don't see the pots. :)

Thanks to you folks for your input. It's a big help to me.

Smurfsdad

I've done it and they did not thrive so now I plant waterlilies in clay garden soil in black plastic oilpans.