This story is of a teenager who got lost at sea for 49 days before getting rescued. As to how he stayed alive:
He survived by cooking fish he caught and sucking water through his shirt to remove some of the salt.
Catching fish is reasonable given the right equipment, and cooking wouldn't even be strictly necessary in a survival situation. However, a T-shirt will not remove any salt from sea water. To do so requires a special membrane and very high pressure.
It seems more likely that he used a reverse-osmosis hand-pump such as this one or a solar-powered pump.
Alternatively, he may have captured fresh rainwater in his shirt, dependent on the monsoon.
It may be possible to breathe the vapor from sea-water soaked clothing to humidify the air and slow dehydration (the salt doesn't evaporate into the air), but that seems like it wouldn't be enough to make it 49 days. Such a system would be similar to this concept.
Is there a more reliable source of information on how he got his water?