There is no description or explanation, just a video that mesmerized me until the end. It seems to be happening during an ice breakup so there is plenty of debris for it to suck into it's vortex. I suppose it's just a drain hole, but it seems to be actively sucking, not just draining. Well anyway, there is a tremendous amount of force. Try not to imagine a swimmer accidently getting too close. I meant this to be under Science General Discussion.