The
Minrothad Guilds (ship ranks, skills, sailors tricks, merchant prince spells, cargo, ship construction & maintenance, port sizes, weather, navigation, and sea encounter ideas) and
The Kingdom of Ierendi (basic naval combat, interesting islands that could be reskinned) are possible options to look at.
You could also include the destruction of Santorini into the mix (the effects on the ocean, animal life and weather - i.e. dark skies with a taste of ash, warm waters, dead/scarred sea life...etc)
Save Icarus from certain death as the party sees him fall.
Rescue an oceanid from betrothal to a cyclops - she swims to the party's vessel for safety.
Recover the body of Orion after Artemis unknowingly fires a kill-shot at him (depending on which version of the tale you decide to make canon for your campaign).
There are literally 100's of tales that can be infused into the party's voyage.