As long as your devotion to blue is less than five, Thassa isn't a creature. (Each U in the mana costs of permanents you control counts toward your devotion to blue.)
At the beginning of your upkeep, scry 1.
1U: Target creature you control can't be blocked this turn.
NM-Mint - $3.70
Lightly Played - $3.50
Moderately Played - $3.30
Heavily Played - $3.00
Damaged - $2.40
NM-Mint Non English - $3.70
Lightly Played Non English - $3.50
Moderately Played Non English - $3.30
Heavily Played Non English - $3.00
Damaged Non English - $2.40