There was this story in the May 2006 issue of Reader's Digest about a humpback whale that got caught in some crab traps.

"Thick nylon crab ropes, called blue steel because of their strength, wound around the fin, through the whale's mouth and over its head. In some spots the lines sliced so deeply they disappeared into the animal's flesh.
Left like this, the whale would die."

The captain of a charter fishing boat put together a group of professional scuba divers to try to rescue the whale. Two divers went down first. They saw that the whale's "tail was wrapped with about 20 ropes connected to a dozen or so 100-pound crab traps. That's what was anchoring her in place. The weights dragged her tail down at a 90-degree angle to her body. From the tail, the ropes wound upward around her flipper. She was hogtied, and using every ounce of strength just to keep her blowhole above water."

Now here's where the cool part starts to come in. As the divers started cutting the ropes tying the whale's flipper, she stopped moving completely. "Even after they cut her flipper free, she remained still and calm."

The divers went back to talk to the crew, and one of them said, "I think she knows we're trying to help her."

When the two divers went back down, one went to work on the lines in the whale's mouth, and the other cut the ones from the tail. The one at the mouth rested his swim fins against the whale's flipper for leverage. He "floated eye-to-eye with the wounded animal. In utter stillness, with that eye as large as a human fist, the whale watched him as he tackled the lines."

While the two original divers continued cutting lines, two more divers joined them to pull pieces of rope out of the whale's mouth that had gotten tangled in the baleen (the hair-like bristles that a humpback has instead of teeth). The whale opened and closed her mouth, but otherwise remained motionless. The diver working at the tail, named Moskito, actually had to use his knife to pry some of the lines out of the whale's flesh. The entire rescue took over an hour to complete, and had to have caused the whale pain several times as the lines were cut away, but she didn't move the whole time.

When she was "finally liberated, the whale did a shallow dive. Moskito turned around: 'Where'd it go? Where'd it go?' he called.
The next thing he knew, she was coming up from below and straight at him. Hey, I just saved you, he thought, relief turning to fear as she rushed him.
The humpback stopped a foot from his chest. She nudged him, then turned away and swam in a circle around the divers. One by one she grazed by each of the four men."

"She swam with them for a good ten minutes."

Pretty amazing story.