I DO sucessfully overwinter a tropical lilly. I have it in a Durabarrel (plastic whisky 1/2 barrel) with a 2 bulb shop light over it. Leave shop light on 24/7, mid-october to mid-may, sometimes June. Mine won't bloom indoors and the pads get smaller, but it survives! If I put a decent amount of light on it, it might bloom, never invested the $$ to try it. As it is, I most likely pay more in electricity over the whole indoor time then it would cost to just buy a new plant each year. (I believe I paid 25 bucks for it, 4-5 years ago.)
By mid July it's blloming like mad in the pond! Variety, Director George T. Moore, bright green pads with light speckling, brilliant purple flowers with yellow center. Bloom all day long which is one reason I really like it. My hardy lillies bloom in the morning and are shut by noon or so.
Back to floaters, sorry!
I've never tried lettuce or hyacinth in the barrel w/shop light cuz I don't want them shading my lilly. Perhaps I'll try them indoors in their own barrel this year, if I'm not too lazy. When I tried them before, it was in a barrel by a window, but the only place my wife would let me keep it wasn't a very sunny location. If you get enough sun I guess it should work.