1. Deep Ocean: 
          
          #1E4D5F
        - A rich, deep blue reminiscent of the depths of the ocean.

2. Sea Foam: 
          
          #77B5A2
        - A cool, calming green that evokes the gentle movements of the sea.

3. Coral Reef: 
          
          #FF7F50
        - A bright, pop of orange that adds a burst of energy to the palette.

4. Arctic Ice: 
          
          #B2DFDB
        - A refreshing light blue that brings to mind the crisp, clean air of the Arctic.

5. Slate Gray: 
          
          #708090
        - A cool, neutral gray that provides a sophisticated backdrop to the brighter colors.

6. Steel Blue: 
          
          #4682B4
        - A subdued blue with a hint of gray that adds depth and complexity.

7. Glacier White: 
          
          #F8F8FF
        - A pure, crisp white that provides a clean, modern feel.

8. Midnight Black: 
          
          #000000
        - A classic, bold black that adds depth and contrast to the palette. 

This cool tone with a pop color palette is perfect for a free diving app, evoking the beauty and mystery of the ocean while providing a modern, energetic feel. The bright Coral Reef adds a pop of excitement, while the cooler tones of Deep Ocean and Sea Foam provide a calming, soothing effect. Arctic Ice and Slate Gray add depth and complexity, while Glacier White and Midnight Black provide a clean, modern feel.