Re: Now if there was a way to talk to people in far away places...
To put it bluntly, the sky is full. There is simply no more capacity in the air over London and South East of England, Holland, New England, Tokyo metropolis and to a lesser extent other large metropolitan areas.
Having flown in it, I can assure you it is mostly empty. The reason you see aircraft "stacking" is because there are no runways on which to land them. Aircraft are really tiny in comparison with the amount of air around and even with the spacing required by old-fashioned ATC systems they can get pretty close. The FAA is working on bringing down the separation requirements and even our Air Traffic guys are working on "Continuous Descent Approaches" where the aircraft are sequenced from way out over the sea to avoid the "stacking" problem.
It is a Spruce Goose NG - a flying boat,
The reason for Flying Boats in the 1930s-1940s was because the technology did not exist to make sufficiently robust undercarriage in the absence of long hard runways. Spreading the load over a hull made it much easier to build heavier aircraft. It also avoided having to build a really long runway or deal with crosswinds, whereas after WWII there were loads of long runways and lots built on the three-runway military pattern, together with a wide range of heavy duty tyres and landing gear. Better piloting techniques and the increase in nosewheel rather than tailwheel aircraft (more tolerant of a crosswind) sidestepped the drawbacks which had driven the use of flying boats.
The penalty of that huge hull is massive drag, as you note it would mean aircraft would be much slower but they would also burn huge amounts of fuel. Not many people would be keen on a 24 hour Atlantic Transit that cost £2000 for a cattle-class seat!
If you do a seaplane rating you will also find there are distinct limits on how rough the sea can be for a landing, so you would need to build massive (really massive) artificial harbours.
The Caspian Sea Monster and other ekranoplanes require very smooth water so are not really relevant to North Sea/Atlantic/Pacific operations. Inland waters only really.