Ultimately, Underworld God Hades and Sea God Poseidon "joined hands" and left in what could only be described as a relatively "harmonious" manner.
But as to whether there was genuine harmony between the two gods, that was a question only the major deities of the Greek Celestial Court could answer.
The moment they could, Underworld God Hades and Sea God Poseidon hurried off to their respective domains to make sure their "territories" were incredibly secure, without the slightest hint of trouble. Then, without planning it, they both headed to the headquarters of the Divine Court, where Divine King Zeus resided.
By the time Sea God Poseidon arrived, he saw a situation that was as bizarre as it gets, a downright standoff, for heaven's sake.