Calusa Shell city - overview

Our assignment in February2017 as a student of concept art was to create concept art for a society that has to deal with a natural disaster. It's a disaster that returns every x number of years. My concept: the exoplanet Calusa is victim of heavy tides, caused by the arrival of a huge planet. The result: a tidal flood with heavy currents, no fish in the sea, no possibility to go into the water, ... The calusa's depend on the help of 'urchies'. They live in a city on rocks, made of the materials/shells they found during low tide. I found the name 'Calusa' during my research. They were the native American people of Florida's southwest coast, who used shells in their daily lives.