So I've been watching as the lagoon gets drained, wondering how deep it actually is. The River's of America is only something like 4-6' if I recall from other reports... but the lagoon in DCA is much much deeper.
Check out this photo from one of the MA stories
With men standing there you can get a real perspective to the light fixtures that were in the water. The lagoon looks to be at least a good 12+ feet deep in the middle.
So why do you think DCA's was built so deep to start with? That's way more then any boat draft you need unless you have a massive boat needing bouancy to stay afloat... 'headroom' for future mechanical gear?