Conversation so far:
When did the Golden Age begin for Aquaman?
For Aquaman, the Golden Age began in November 1941
What happened with Aquaman in #73?
Aquaman's first origin story was presented in flashback from his debut in More Fun Comics #73
Who was Aquaman's father?
Aquaman's father was a famous undersea explorer
What was Aquaman's father's name?
His father's name is not given, but Aquaman says If I spoke his name, you would recognize it.“
What did Aquaman's father do?
His father was a famous undersea explorer
What city did Aquaman's father discover?
He discovered the underwater city of Atlantis

Question: What did he find there?
Self-contained rewrite: What did Aquaman's father find there?