What's your alternate theory here? That a ship from the 1800s sailing through tropical oceans is going to fill its bottles with zero humidity air before throwin

What's your alternate theory here? That a ship from the 1800s sailing through tropical oceans is going to fill its bottles with zero humidity air before throwing them overboard? Of course there will be water inside the bottles, the air in the bottles will be humid, and temperature cycling through the seasons and from local weather will lead to formation of dew inside the bottle from time to time.