These tubers keep washing up on the shore of a small slough near me in west central Minnesota. They're interspersed with lots of what I think are smaller Stuckenia pectinata tubers and stems in wind-blown mats but are different enough to make me think it's another species. The only other submerged aquatic plants I've seen are a Potamogeton, maybe perfoliatus, and hornwort.
As a side note these kinds of sloughs are pretty interesting because of the year-to-year changes they go through, being shallow enough to freeze to the bottom and kill off most of their inhabitants every winter. Usually there's just fathead minnows and brook sticklebacks but this year a pretty substantial white sucker population has emerged from the ice -- hopefully some made it too!