I was never able to find "in water" or "tanning ledge" specific umbrellas. The consensus seems to be to use standard patio umbrellas that have powder-coated or anodized aluminum poles. No steel, it rusts, and no wood, it expands and gets stuck. Apparently, most umbrellas also have a standard pole width of 1.5 inches. We got our umbrella from Amazon and it fit perfectly. As for what size hole to drill, not sure. I would select an umbrella sleeve that matches your decor, and then follow the instructions. Our PB installed our sleeve.