Storm & Flood Damage Recovery in Tybee Island, GA

That is the design working as intended. On a barrier island, elevated construction puts the living floor above the design flood level and leaves the space below as breakaway or open enclosure, which is expected to flood. It is why storage, mechanical equipment, and finished space below that level are a bad idea however convenient they seem. The house being untouched while the enclosure floods is a success rather than a near miss.

Not particularly, and it is a common assumption. Tidal water reaches the marsh side as readily as the ocean side, and the marsh drains more slowly once it is in, so water can stand longer there. What matters is your elevation relative to the tide, not which direction the open water lies. The beach and marsh sides are two routes to the same water level.

Less than owners expect, and metal fares worst. Salt remains after the water evaporates, keeps drawing moisture back into materials, and corrodes fasteners, wiring, and mechanical components for years. Porous materials that were submerged generally come out rather than being dried in place, and surfaces that stay need rinsing and testing. A scope written for clean water will look complete and then produce corrosion and electrical problems months later.