Busy day, sorry, so have a hymn to Poseidon, hidden away in Aristophanes's The Knights. It's sung by two of the characters and is quite lovely, so I thought I'd share.

Oh, Lord! Oh, Lord, protector and lover of horses!
Lover of the brazen clang and thud of the horses’ hooves, lover of the horses’ neighing. Lover, too, of the swift war ships with their blue emblems of rams at the prow!
Oh, God, whose heart gladdens at the sight of the rich booty those ships carry! A heart that also gladdens at the sight of young men in contest, particularly when they climb proudly upon their chariots chasing their Fate -victory or defeat, no matter!
Come, God of the horse, come now and join our dance!
Poseidon, God of the golden trident, come join us!
God, chief of the dolphins!
God whose name is praised at Sounion!
God, son of Kronos, Geraestus!
God, most loved by the folk of Phormion to whom you granted a naval victory!
God most loved by all the citizens of Athens at this hour of their naval need!