The study tested how well guppies can survive in different levels of saltiness in water. They found that guppies can live in water with up to 28 parts per thousand salt if they are put directly into it. But if the saltiness increases gradually, they can survive in water with up to 38 parts per thousand salt. Guppies started dying when the saltiness reached 10 parts per thousand if they were put directly into it. They also found that guppies can have babies in water with up to 20 parts per thousand salt, and the babies can survive in the same salty water.