This page of the trophy guide to Death Stranding has a detailed description of Soak and Sigh trophy. You get this bronze trophy for bathing in a hot spring for the first time.
There are several hot springs in the game and you can choose any of them to unlock this trophy. In our case, we chose The Crater Digestive Bath located in the central region. This hot spring is located southeast of the Distribution Center South of Lake Knot City and is adjacent to the Film Director.
You can see this hot spring from far away. The hot spring marker doesn't have to be visible on the world map immediately. However, it appears on it after using the scanner.
Enter the hot spring. If the Timefall is currently happening, you need to wait until it stops. If it is not raining, hold Circle to interact with the hot spring.
The main character will undress and begin to bathe in the hot spring. Don't get out of it - wait a few seconds to unlock the trophy.