The Hughes H-4 Spruce Goose was 9.1 meters.

The Sanders Roe Princess was also pretty high up there, but I couldn't find any numbers.

9.1 meters (30') is the fuselage height for the H-4. I believe that's not above water, but dimensions to bottom of the hull.

Interesting 360 view of the H-4 Cockpit: Spruce Goose cockpit by Larry Lohrman | Spinattic.com

Fuselage height was 30' on the Goose (the kinder of the nicknames given it), but I believe that was on land.

Interesting size comparison between the H-4, A=380, B747(-400), and the AN-225: http://www.aerospaceweb.org/question...comparison.jpg