Continuity mistake: Chief is tied to his kennel around the collar. But when Copper cuddles up to him for the first time, the rope tied to his collar disappears for a shot. (00:10:35)
Continuity mistake: The buttons on Amos Slade's shirt repeatedly change sides between shots throughout the movie. One example is while Copper and Tod are swimming, when Amos tells Chief that Copper has strayed off again, the buttons on Slade's shirt go from being on the left to being on the right, then back to the left again. (00:21:50)
Continuity mistake: After Tod accidentally causes mischief in the barn with Abigail and the chickens, Widow Tweed picks Tod up and we see the barn doors with its double-z panels, but when Tweed puts Tod down and he scampers outside, those double-z panels are facing the opposite way. (00:13:25)
Continuity mistake: While Tod visits Copper, who's all tied up, when Tod starts walking over to the big snoring dog we see the rope on Chief's barrel, but as Copper warns him that Chief is cranky the rope has vanished, though it reappears in the next shot. (00:23:10)
Continuity mistake: After Dinky tells Big Mama and Boomer his idea, when Boomer flies over to Widow Tweed's house to knock on the front door, the water pump is beside the tree at the left side of the house, but when Widow Tweed opens the door and hurries over to the "pesky" birds, the water pump is now at the right side of the house. It continues to change its position in front of the house in following shots. (00:07:50)
Answer: Since we don't really know how he died, he could have drowned and not died on impact. Bear may not have been a strong swimmer or sustained too much injury from the gunshot to swim to the surface. However, in physics, force = mass * acceleration and thus larger creatures will hit the water with greater force than small creatures (as the old cliche goes; the bigger they are, the harder they fall). So it's possible for Bear to die on impact and not Tod because of his larger size.
Bishop73