The US military actually used concrete 'blockships' to create an artificial harbor for use in D-day. Doesn't need to be aircrete to float if correct shape! ht

The US military actually used concrete 'blockships' to create an artificial harbor for use in D-day. Doesn't need to be aircrete to float if correct shape! https://warfarehistorynetwork.com/daily/d-days-concrete-fleet/ https://warfarehistorynetwork.com/daily/d-days-concrete-flee...