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.
Near Mint - $4.25
Lightly Played - $4.00
Moderately Played - $3.50
Heavily Played - $2.50
Damaged - $2.25
Near Mint Non-English - $4.25
Lightly Played Non-English - $4.00
Moderately Played Non-English - $3.50
Heavily Played Non-English - $2.50
Damaged Non-English - $2.25