Maelstrom is a boat ride that travels back in time in Norway. There are trolls, you travel backwards for a while, there is a drop and then after it is over, you end up in a theatre with a short film about Norway. Some people skip the film, but if you have never seen it, it isn't too long.
It is a ride where you can get fastpass, but if you arrive early after WS opens it doesn't seem too busy. As someone said it is at the back of Norway, inside a building, and not an easy "in your face" doorway.