An action camera is a camera with a deep focus that doesn't require focusing, but prevents the subject from focusing at close range (within 60 cm in theory for the GoPro® camera) and therefore cannot be used for underwater shooting.

Using a standard macro lens for a compact digital camera would not help the situation, as it would create vignetting and a very shallow depth of field, preventing comfortable focusing. The SD UCL-G165 lens is what we call the "wide-angle lens", specially designed for action cameras based on their optical characteristics. The depth of field underwater will be 5 cm to 35 cm if you use the GoPro® HERO6 Black lens, which supports a minimum focusing distance underwater for capturing photos/clips.