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 - $6.40
Lightly Played - $6.10
Moderately Played - $5.70
Heavily Played - $5.10
Damaged - $4.20
NM-Mint Non English - $6.40
Lightly Played Non English - $6.10
Moderately Played Non English - $5.70
Heavily Played Non English - $5.10
Damaged Non English - $4.20