It's been a while since I posted a process post like this for Theurgy so here we go!
Brushes used:
Sand Brush (texture on beach): https://assets.clip-studio.com/en-us/detail?id=1881938
Surface water brush (for the shiny parts): https://assets.clip-studio.com/en-us/detail?id=1999781
Water surface brush (for the darker parts): https://assets.clip-studio.com/en-us/detail?id=1825462
Tree shadow brush: https://assets.clip-studio.com/en-us/detail?id=1610988
Stones / Pebbles brush: https://assets.clip-studio.com/en-us/detail?id=1825675
Pattern on Des's shorts: https://assets.clip-studio.com/en-us/detail?id=1718038
Grass and ground texture: https://assets.clip-studio.com/en-us/detail?id=1732795
Cloud brush: https://assets.clip-studio.com/en-us/detail?id=1723992
Leaves brush ( i think... ;-; I have a lot of these downloaded so im not positive which I used lol): https://assets.clip-studio.com/en-us/detail?id=1714347
The brush I used for the bushes seems to have been deleted, but you can find a lot of these types by searching for "leaves brush" or "tree brush" or "bushes brush" etc!