Based on a plein air painting created on Florida beaches. Notice photos have not captured the 'feeling' I had on location. Photos have more contrast, as an a artist you will learn to see more color and nuance on location. You can direct this in your paintings based on studies and notes taken on location.
Create a good value plan (simple grouped shapes) and use color shift to make believable waves and shore. Try to use compressed value (of the 3 main groups of light, medium and dark try using only 2 main value groups).