Over most parts of the water lilies range, the rhisome of a water lily
can be vulnerable to freezing killing them in a hard Winter.
Additionally, many critters will go to town grazing on easily reached
stems and rhisomes, ducks can easily destroy a water lily in shallow
water.

Many water lilies are very vigorous, to plant them shallow and they
would soon dome up forming a cabbage like heap, with so much foliage
exposed, bugs like aphids and leaf curling viruses can tear through a
well exposed plant.

When you changed its planting depth, you probably saw the water lily
'stall' where its growing habit was changed drastically, its not
unusual for water lilies to appear to stop growing when something
drastic changes, like its roots are damaged or its depth is changed
suddenly. Most water lilies do like being started shallow, when
there's plenty of foliage forming, stepping it into deeper water in
steps of 6" at a time will probably keep it ticking over better, most
water lilies will look better if they have plenty of depth to spread
in, say about three times the width of a lily pad as a rough depth
guide

Regards, Andy
http://www.members.aol.com/abdavisnc/swglist.html
http://community.webshots.com/user/adavisus
(photo albums of aquatic plants and descriptions)

Carl Beyer wrote in message ...
I have a hardy lilly in my little pond, when I lowered it earlier this
year it nearly crapped out, so I raised it back up to about an inch or
two under water and it has gone like gang busters. Now it is fading a
bit (it has been hot in LA, though).

Anyway, just wondering why the say to put it deep, yet mine seems to be
doing just fine near the surface.

Carl