A jet boat is direct drive, any time the engine is running, the impeller is spinning, and it is making thrust. Unless you precisely have the reverse bucket dead center, and the steering wheel dead center, the boat will MOVE, even in “neutral.” (See above video about Jet boat operation)
This is a HUGE BENEFIT once you master it, and realize how it works, but can be frustrating at first, but you must always remember, the boat will make thrust is the engine is running. Never leave the helm with engine running, the slightest turn of the steering wheel will send the boat spinning. (Again, this is amazing if you use it properly, but not sitting at the dock).
If you want to sit perfectly still, KILL THE ENGINES ENTIRELY.
It is also highly recommended you learn to take advantage of the fact that the gear shift in a Vortex/Rotax is fully variable, all the way from reverse, through neutral, to forward. You have full control, we highly recommend you read this guide to understand, and use this feature, to fully control your boat. If you learn this, you will be running circles around any other boat type pronto!
https://www.facebook.com/groups/ChaparralVortexBoatOwners/permalink/1734862313486180/