海かい流りゅう瓶びん

noun

drift bottle

A bottle released into the sea to study ocean currents, often containing a message or tracking information.

• 海かい流りゅう瓶びんを海うみに流ながして、海かい流りゅうの動うごきを調しらべる。

  They release drift bottles into the sea to study the movement of ocean currents.