Vehicle Controls

I’ve had Garry’s Mod for a while now and I haven’t really done anything productive, but now that its summer I want to get into building vehicles. I can design and build just fine, but what I want to know is how to give my vehicles controls. I know I can just use thrusters and hoverballs but I’d rather not if there’s other options. I’m working with boats and a good example of something I’d like to build is this: http://www.garrysmod.org/downloads/?a=view&id=65169 It’s a simple boat but from what I’ve seen, it moves without hoverballs or thrusters. So what I want to know is how they’re doing this and how can I do it. A simple link to a previous thread explaining this is fine too.

Somehow I think the creator turned off the thruster sounds and made whatever thrusters or hoverballs it has invisible. And don’t spring for it, NPCs have odd glitches when on top of floating objects.

That’s what I thought at first but because it doesn’t work at on land or in air I don’t think it could be thrusters or hoverballs. And I know about npcs on floating objects, the main purpose of my boats is so when I figure out Gcombat better I can make battleships and the like.