Have you ever held your hand out of a car window and felt the wind pushing it up or down? That's because the air is moving around your hand and changing the way it moves. It's kind of like a game of catch: if somebody throws a ball at you, you have to move your hands to catch it, right?
Now, imagine if you had a boat floating in the water and you wanted it to go faster. You might think that the best way to do that is to put a bigger engine on it, but there's another way to make it go faster: by making it more aerodynamic. That means changing the way the air moves around the boat so it can move more easily through the water.
An aerodynamically alleviated marine vehicle is a boat that has been designed to be more streamlined, or more like a torpedo. The shape of the boat has been carefully engineered so that the wind and water move around it in a way that creates less resistance. That means the boat can go faster with the same amount of energy from the engine.
Think of it like this: if you're swimming in a pool and you're wearing a big, poofy coat, it's going to be harder to move through the water than if you're wearing a tight, streamlined swimsuit. The same thing applies to boats. By making them more streamlined, they can move more efficiently through the water and go faster with less effort.