漂流瓶

piāoliúpíng
message in a bottle

CEDICT

drift bottle (bottle with a message inside, which is set adrift on the ocean)

Wiktionary

Entry Composition

1 漂流 piāoliú
  1. to float on the current
  2. to drift along or about
  3. rafting
=2 瓶 píng
  1. bottle
  2. vase
  3. pitcher
  4. classifier for wine and liquids

classifier: 個
=2 瓶 píng variant of 瓶 píng