This grower is fairly sure of this plant identification.
Plant growing in a bucket, ready for a new home
Nuphar polysepala (Water lily). A floating, water plant from North West America.
They will flower in the shade and some species are suited to being planted in slow-moving water. They prefer to be planted in pots of rich soil and then carefully submerged. You can propagate by division.
Grown for their floating foliage and spherical flowers.
Italics = data drawn from parent genus or speciesView Full Plant Finder Record