What makes ships mysteriously slow down or stop, even though engines are running?

Source: Science Daily

What makes ships mysteriously slow down or even stop as they travel, even though their engines are working properly? This was first observed in 1893 and was described experimentally in 1904 without all the secrets of this ”dead water” being understood. A team has explained this phenomenon for the first time.

https://www.sciencedaily.com/releases/2020/07/200706152701.htm