The whole swimming tire thing is kind of a fascinating mystery to me...2 cases in point.
1) Kenda Bearclaws did not swim a stroke for me, but will swim a little on MattO's MudOx
2) MightyMaxIV had all Vampires at one time, and while they swam, he had a hard time turning/controlling them, however; they swim/turn well on the Hustler. The only difference we can think of is that the Hustler has more distance between the front and center axle, than center and rear.
So I think in addition to tread patterns, vehicle type must also be considered. A tire that swims on a 8x8, may not swim on a Max II for instance......it's all one big experiment.