Marriotts is not a very difficult rapid, however you have to choose your line and paddle convincingly to avoid some of the messy stuff in the centre. The rapid snakes right and then left and the gradient is fairly flat, so you can read the lines well. The easiest option is to hug the inside of the bend (keep right) and then move back into the centre as the rcurrent starts to swing left again.
In low conditions stick to the main current and follow the flow. In very high conditions it gets easier and the lines open up gving you more options.