Hamilton averaged 9.5 points and 4.3 rebounds last year while at Boston College.
Reese is the brother of incoming women's basketball guard Angel Reese.
Watson averaged 36 minutes per game last season, posting 13.0 points, 3.6 rebounds and 3.4 assists.
The Terps are thin at the front-court. Here's who they could add.
Chol Marial, Donta Scott and Joshua Tomaic remain the Terps' only frontcourt options for next season.
The forward's decision leaves the Terps' frontcourt depth thin.
Aiken committed to Seton Hall, leaving the Terps with two open scholarships.
Smith earned first-team all-Big Ten honors after averaging 15.5 points and 10.5 rebounds this season.
Hamilton averaged 9.5 points and 4.3 rebounds as a sophomore with the Eagles.