sea lane vs ship route

sea lane and ship route both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea lane	Yes	No	No	No
ship route	Yes	No	No	No

As nouns, sea lane and ship route are synonyms defined as:

sea lane and ship route: a lane at sea that is a regularly used route for vessels

Other synonyms of sea lane include seaway, trade route.

sea lane (noun)	ship route (noun)
a lane at sea that is a regularly used route for vessels	a lane at sea that is a regularly used route for vessels