i think there is a big difference: kalmah (at least some of them) seem to have a direct connection/affinity to swamps, which is obviously not the case in CoB and the lake.
as much as I know, CoB chose the name in referrence to some murders, which shall show how mean CoB are or something like that
Kalmah's swamp theme does actually MEAN something particular to some members - that's an essential difference, imho