Ironically, looking at a tropical theme might make you worry about heat. While the aesthetic is "cool waters," you need actual airflow to keep your components from overheating. Ensure your chosen case has mounting points for at least three 120mm fans on the side or bottom (intake) and a radiator mount on the top (exhaust).
Configure more intake fans than exhaust fans. This prevents dust and humid air from seeping in through unfiltered gaps. pc case maldives