https://wccftech.com/sea-of-thieves-shrouded-spoils-update/

These days most games try to avoid fog as much as possible, but the next Sea of Thieves update is embracing it. Per Rare’s latest dev diary, Sea of Thieves’ Shrouded Spoils update will add roving fog banks, which can strike at any moment and make navigation a rather tricky affair. You can get more details below.

Here’s how Sea of Thieves executive producer Joe Neate describes the fog mechanic: