Science fantasy is sort of a strange genre, and not one everyone recognizes. To some, if it isn't hard SF, it's fantasy by definition. That means any SF with faster than light travel, battles with spaceships, or what have you. All of these things are actually fantasy because physics rules them out. But most agents that say they represent science fantasy are explicitly including or excluding hard SF, not the other way around. If your manuscript is "space opera", then it's probably science fantasy.
Still, I'd only call it that if the agent uses the term. Else, I'd just say SF.