Apparently chloroplasts are independent living organisms. They reproduce on their own and have their own DNA. They also do not release any bi-products of photosythesis that are harmful to animals. What they do release are oxygen and sugar molecules. Oxygen can be used to suppliment the oxygen intake of the animal and sugar can be readily used to provide energy.

Choroplasts did not start off in plant cells. They were ingested by single cells organisms. This is why they have two cellular membrains, which make up the rigid cell walls in plants. One cell membrain came from the chloroplast and the other came from the single-celled organism. Animal cells are also much bigger than chloroplasts.

This means that we can put choroplasts safely into animal cells. The choroplasts will multiply to create more sugar as long as sufficient water and sunlight is available. This would decrease the amount of food an animal or human would need to survive. It would also change their skin color. The options available range from green to blue to purple. Lol, a new race to discriminate against - the purple people...

Anyway, this would allow people to live underwater or in environments where no or very little oxygen is available. This means a shift in population density to areas that wouldn't normally be inhabited by humans. All they would need to survive is a light source and water. There is no way to tell for sure, but I suspect that no one participating in the change would have to worry about drowning or starving again. However, if it's not as effective as I'm thinking, then just use it as a supplement.