You aren't taking into account the degradation sea water has on infrastructure. The pounding waves and salt would most certainly make the buildings unsafe.
Well, the concrete that actually takes all the load would be safe; that's how pretty much any caissons or foundations in water are built anyway. Electrical delivery would have to be completely re-thought and redeployed. There wouldn't be 'pounding waves' since the rest of the city would be diffusing large waves.