Captain Lash (1929)

Lash is the head coal stoker on a steam ship whose shipmates have nicknamed "Captain". Lash somehow grabs the attention of society dame passenger Cora Nevins. Nevins is actually a jewel thief who's lifted diamonds from wealthy passenger Arthur Condrax. She needs Lash to aid in sneaking the "ice" ashore at Singapore. Cocky is Lash's concertina-playing buddy and uses it to signal Lash.