Good visuals in that 7m clip. Note, however, that there was not any discussion regarding permeation of the seawater via an end-run - rather, an under-run - around (under) any seawalls. Miami Beach and all of south Florida can raise sea walls until they reach the top of skyscrapers - and still the sea will come in. Hydrodynamically, the only card that man has in south Florida is the hydrostatic pressure of fresh terrestrial water maintaining enough pressure to resist the pressure of seawater at any land/water interface.
HOWEVER...even that is not enough. The single problem that balancing act can solve is keeping well water, etc., from becoming brackish or saline. Now, that's an important enough problem to resolve and it can be done...as long as freshwater drawdown is kept low enough so that the needed hydrodynamic pressure is maintained. BUT - that fresh water "piston" cannot keep any higher-level seawater away. If this is difficult to visualize, imagine a body of water - call it an aquarium, or water glass, or whatever you like. Place a barrier across half of it....but punch a lot of holes in the underwater portion of that wall to represent the porous nature of Florida's limestone. Now raise the level of the side you designate "ocean". Of course, effectively instantaneously the water level equalizes on both sides of your model sea wall.
I've little interest in a bargain piece of south Floodrida, thank you very much.