A cheap, endearing, creaky actioner from Monogram which gave a leading role to Lon Chaney Jr early in his career - so early she was billed as Creighton Chaney. He gives this movie a point of difference - not a conventional leading man, even in his early days, with his lump features. But he has kind eyes and presence and works quite well with Sally O'Neill, the female lead.
The plot is simple and the action clocks in at under an hour. Chaney's a sponge diver who wants to make money to marry his girl; a dodgy ethnic is trying to stop him.
This reminded me a lot of Lovers and Luggers, the Australian film - scenes of divers going to the bottom of the ocean and getting bends, romance with a feisty girl, ethnic villain. That was based on a novel which was published in 1928; it's entirely possible the writers of this came up with the same tropes independently.
It's no classic, but there's lots of location work and it zips along. It was liked enough to be remade in 1948.