Gods and Opalescence
This depends on the order the cards entered the battlefield and what your devotion is.
Both Opalescence and the Thassa's “I'm not a creature if your devotion isn't high enough” effects apply in layer 4. There's no dependency, so we apply them in timestamp order.
If the god entered the battlefield first, then Opalescence has a later timestamp, so its effect will apply after the god's effect. No matter what your devotion is, Thassa will always be a 3/3 creature (although if your devotion to blue is 4 or less, Thassa will not have the god creature type).
If Opalescence entered the battlefield first, and your devotion to blue is five or more, then Thassa will be a 3/3 creature (Opalescence's effect applies later in later 7b and will still make the Thassa into a 3/3 instead of a 5/6).
If Opalescence entered the battlefield first and your devotion to blue is four or less, then Thassa will not be a creature. In layer 4, we apply Opalescence's effect first (making it a creature), then we apply Thassa's effect and Thassa is not a creature. Since Thassa is not a creature, it won't gain a power and toughness in layer 7b, so Thassa would end up as not a creature.
In short: Thassa will be a 3/3 creature, unless Thassa entered the battlefield after Opalescence and your devotion to blue is less than four, in which case Thassa will not be a creature.
Nathan Long
Wizards.Com Boards NetRep