水みず先さき案あん内ない船せん

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Meanings

1

noun

pilot boat

A boat that carries a maritime pilot to and from ships entering or leaving a port.

water

先before, ahead, previous

案plan, suggestion, draft

内inside, within, between

船ship, boat

水みず先さき人にん
水先人 is the maritime pilot (the person), while 水先案内船 is the boat that carries the pilot.

Compound of 水先 (mizusaki, 'course of a ship') + 案内 (annai, 'guidance') + 船 (sen, 'boat').