There is no record of anyone being killed by a mother black bear defending her cubs, and attacks are very rare. ... Startled black bears run away, often to a tree. By contrast, a startled grizzlies may charge and occasionally attack, making grizzlies over 20 times more dangerous than black bears.
A black bear's first line of defence is retreat, but grizzlies, especially sows with cubs, can be very aggressive towards other bears and people they perceive as threats. Grizzlies are not good tree climbers, though it's important to note that they can climb trees. ... It is a sign of curiosity, not aggression.
According to Bear Life, "North American Black bears like to swim. If there is water where they live they will exploit it for food. Since bears like to hunt fish, they are not shy of water. In fact, their baby cubs take to the water quickly."Feb 29, 2016
Black bears are very opportunistic eaters. Most of their diet consists of grasses, roots, berries, and insects. They will also eat fish and mammals—including carrion—and easily develop a taste for human foods and garbage.