Watson, 31, is a former seventh-round pick of the Buccaneers back in 2010. He wound up playing out his rookie contract with the team before signings on with the Jaguars in March of 2014.
After brief stints with the Cowboys, Patriots, and Broncos, Watson signed a three-year, $6 million contract that included $1 million guaranteed with the 49ers last year. Denver traded for Watson back in April for a fifth-round pick but was cut last during the preseason.
Seattle signed Watson to a contract a few days ago.
In 2018, Watson appeared in four games for the 49ers and recorded six total tackles, two sacks, and one forced fumble.