If you don't want have water in your base during storms, the ground level of your building must be at minimum at 6 or 7 stone walls from the water level
Hmm, my
island base isn't that high ground and the storm waves only happen in one corner of the house as far as I have seen. That corner (with beds) practically has a foundation on the ocean itself. Then again, one side of the island base is "covered" by very small mini island which only has one lighthouse (with workbench inside) in it to prevent monsterspawns. Now that you mentioned it, I'm not sure if I have been wandering around the island during the storm to see how far the waves go elsewhere.
I'm not quite sure what things
definitely stop monster spawns, but for me hiding workbenches all over the area seems to be the most efficient way. I have hidden them inside the bushes, behind the trees, under the floors or made small useless "sheds" or the likes for them. You have to pay attention to not miss _one_single_inch_ inside your base area or monsters might spawn. I keep cheking the workbench coverage by running around with roof piece selected in my hammer, which shows you the area of effect. I once missed little tiny area and that kept spawning monsters all the time. When I made one extra workbench to cover that area, spawns stopped.
My island base didn't have one single enemy during raids before I pickaxed two huge rocks from the lighthouse island. I tested it by force starting the raids in creative mode like 10 times and had few normal ones happening too in between. Nothing ever happened. After destroying those two huge rocks on the other end of the island, I started randomly getting few (like one - four) monsters in the lighthouse island and those were all blobs/oozers from the swamp. I also got one flying raid. Monsters always appeared to the part of the island that had previously been blocked by those rocks and I think my island workbench may not be covering that spawn point. I should make another one and try if it works whenever I would have time.
EDIT: Since the raid focuses at me and not to my property, theoretically I could probably stop those little raid spawns by moving my base (aka location where I spend most time) to the other end of the island? Now that I think of it, those times when nothing happened, I may have been testing it somewhere else than inside my actual house. Or it was the effect of removing the rocks
One way to prevent waves inside the base could be building bit further away from the shore? Haven't tried that yet since I haven't found a proper island for it.