What should i do if my fluid falls through an object? I want to make a shoreline scene, but my fluid always falls through my "floor". I dont know why (it's my first time with fluid sim). Does anybody know what the problem is?
Try increasing domain resolution. Notice resolution has two settings : one for render (= what you see when you press f12), and one for preview (= what you actually see in your screenshots).

However, fluids are designed for smaller scale simulations (like, a bathtub, or maybe a small swimming pool). Maybe it's not the best solution for this case.