Preheat the oven to 350°F (175°C) and grease two 8-inch cake pans.
In a bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a mixing bowl, beat the butter and sugar until light and fluffy.
Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.
Alternately add the dry ingredients and buttermilk, mixing until just combined.
Divide the batter into two portions. Tint one with blue food coloring and the other with a mix of blue and black for a deep ocean effect.
Swirl in melted white chocolate for a marbled ocean look.
Pour into cake pans and bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean.
Cool cakes completely before frosting.
Tint buttercream frosting with blue and black food coloring for an ocean gradient effect.
Apply a crumb coat of frosting, then smooth with a cake turntable.
Mix tonic water with neon food coloring to create UV-reactive glowing accents. Pipe onto the cake for glowing waves.
Dust with edible pearl dust for a shimmering ocean effect.
Chill the cake for at least 30 minutes before serving.