A juvenile monk seal that was one of four born in 2017 has died.

The seal was found on Christmas Day floating listlessly in waters near Hawaii. It was brought to the National Oceanic and Atmospheric Administration’s monk seal treatment facility on Oahu. It died on Friday from what experts believe might have been a severe infection.

The seal, RJ16, was commonly known as “Kahulu.”

A blood test indicated it had an infection of unknown origin.