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 - $5.70
Lightly Played - $5.40
Moderately Played - $5.10
Heavily Played - $4.50
Damaged - $3.70
NM-Mint Non English - $5.70
Lightly Played Non English - $5.40
Moderately Played Non English - $5.10
Heavily Played Non English - $4.50
Damaged Non English - $3.70