The Aquasport line came in a wide variety of dials and case styles. The product line was launched around 1941 and featured steel screwback cases and colorful dials. There was also a watertight tank model:
Your example is sort of a second-generation Aquasport, circa 1944. The dials got a little more austere and came in black or white with lumed hands and arabic numbers. These are relatively common; you'll also find them with a 24-hour dial:
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