While Mia was eating the placenta, there was blood around her mouth. Just a few seconds later, there was no blood on her face after she picked up her baby.
Assuming she is adrift in the Atlantic ocean, the water temperature would be around 15C / 60F even in summer. Hypothermia would be lethal in about one hour in these conditions.
Mobile network and communications doesn't work inside the cargo container and on the high seas.
Mobile phone is unable to work as long as shown in the film in high humidity and without recharging.
While this is an interesting story, there are many plot holes. The biggest of them would be a steel shipping container floating. While it is plausible that these shipping containers (some of them being airtight) might float, with the number of holes in the sides of the container that she was in, there is no way this container would still be floating all those days.