Okay, I'll jump in on this one, because I thought I was going to find out the answer to your question last week.
We were anchored out in a cove on the west coast of Vancouver Island last week. There are lots of black bears on Vancouver Island. In fact I think it is black bear heaven. I've never seen as many black bears anywhere else. The first evening that we were there, we saw a large black bear feeding on berries near a camping area on shore. There was also a small bear that the larger fellow chased up a tree. They were about 1/4 mile away, and we enjoyed watching them through binoculars until dark. Late afternoon on the following day, I saw the large bear coming around the cove towards where our boat was anchored. He swam through several small bodies of water instead of going around them. He looked more comfortable in the water than a black labrador. When he got down wind of our boat he started sniffing and swam out a few yards towards us (we were approximately 30 yards away from him). For whatever reason, he decided we didn't smell good enough and he turned around and went back.
I think it was fortunate that we hadn't just caught and cleaned fish. We had our garbage sealed in plastic and inside the boat. All of our food was in a closed cooler in the cockpit.
I didn't sleep well that night. I wasn't sure what I was going to do with a 350 lb bear in the cockpit during the middle of the night. It was Canada so you can't carry a gun. I had bear spray and an air horn. Fortunately I didn't have to find out if they would get him to leave. Even if I had scared him out of the cockpit, it would have been like chasing off a sumo wrestler with fangs and claws. He probably could have done a lot of damage to the equipment even if we were safe.
A long winded story just to say that bears can swim really well. If in bear country, don't leave garbage or food lying around and clean up after fishing.
Lyle