It's a very informal and somewhat playful expression, usually used by a child or young adult to compliment their father on their appearance.
Here's a breakdown of the phrase:
* Maldita sea: This is a mild curse word, similar to "Damn" or "Gosh" in English.
* Papá: This means "Dad" in Spanish.
* Te ves bien: This means "You look good" in Spanish.
The phrase implies that the speaker is impressed by their father's appearance, perhaps because he's dressed up or looking particularly handsome. It's often said with a smile and a touch of admiration.