Seeing your obvious interest, hear's an article (
Prototype GHOST military watercraft claims a world's first | Technology ) with large color pictures including the cockpit panel (what...they're building an interior!) and a dry-dock shot which shows the underwater parts that create the super-cavitation drive. I have not seen anything about dimensions other than it had a three-man crew. That made me think thirty feet or so. It does say the a larger version around 150 feet was under discussion. I had not seen the artist's conception of the Ghost in combat that Zathros submitted; that makes me think the underwater pods may be thirty and the above water portion somewhat shorter.