Video shot horizontaly only shows verticaly in AirPlay

Just got my iPhone so I'm still a noob.

First time shooting a video at the park today and I recorded while holding the phone horizontally, but when I put it on AirPlay it was vertical AND sideways (90 degrees off).

I figured out how to edit it and give it a rotate but that seems ridiculous and just wrong.

I'm guessing it's user error somewhere along the lines.