Quoted By:
Brawly's design in the original GBA game is weak as fuck, it fails to convey in any way that he's a surfer.
His gym dialogue gives equal weight to the waves of his seaside town, and the darkness of the cave you explore before challenging the gym. His gym itself is dark and he gives you the badge that lets you use Flash as a field HM move.
If anything, the darkness part outweighs the ocean waves part.