long sea voyage
Rare, literary noun for a long journey by sea. Found mainly in classical or poetic Japanese; in modern language, expressions like 長い船旅 or 長い航海 are more common.
There is a journey sung as 'yashioji' in an old waka poem.
A poetic compound of 八潮, “many tides,” and 路, “route,” referring to a long sea journey; 八 is used figuratively for a large number.