Antediluvian and Before the flood

Antediluvian adjective - Dating or surviving from the distant past.

Before the flood and antediluvian are semantically related. In some cases you can use "Before the flood" instead an adjective "Antediluvian".

Antediluvian and before the flood are semantically related. Sometimes you can replace term "Antediluvian" with "Before the flood", this terms are similar.