Your body may persist as a corpse when you die; but if a corpse is not a person, the Standard Criterion does not imply that you persist as a corpse. It simply does not apply here, for this is not a case in which we have ‘a person x existing at a time t and a person y existing at another time t*’. The presence of bleeding usually distinguishes ante-mortem from post-mortem injuries. The Standard Criterion even allows for you to have different bodies at different times, if at one of those times you are not a person. For all the Standard Criterion says, you may end up as a demented non-person with a different body from the one you have now.
Corpses in water always lie with the face down and with the head hanging. Buffeting in the water commonly produces post-mortem head injuries, which may be difficult to distinguish from injuries sustained during life. Suppose you get a bad case of senile dementia–so bad that you no longer count as a person. However, the head down position of a floating corpse causes passive congestion of the head with blood, so that post- mortem injuries tend to bleed, creating the diagnostic confusion.