The article indicates that the rescue of the teenagers was a surprise when it mentions that Tongan officials had "given up for dead" on the boys and that "funerals have been held." This underscores the disbelief and astonishment surrounding their survival after being missing for 15 months.
If I were stranded on a deserted island, the first thing I would do is find a reliable source of fresh water, as staying hydrated is crucial for survival.
Three things the teenagers did that helped them survive on the island include: 1) Foraging for food such as bananas, coconuts, and shellfish, which provided essential nutrition. 2) Collecting rainwater using coconut shells and hollowed-out tree trunks, ensuring they had a source of drinking water. 3) Building huts out of coconut fronds for shelter, which protected them from the elements.