Mad Max Mermaid

She wasn't meant to be a Mad Max crossover but she kind of ended up there.
The original idea was as follows:
If you are working with a sentient, human natured-esque mermaid it is fair to say that they would fashion tools and weaponry for hunting, protection and possibly battles between tribes. 
What happens to a mermaid who has been injured in battle or by a predator. If they have the ability to create tools they would also find a way to build devices to help their handicapped friends become handiabled.