1. Find one water lily (at least) 2. Put close-focusing/macro lens on tripod 3. Attach polarizing filter to lens 4. Attach diffusion filter to polarizing filter 5. Turn on live-view to compose the shot and manually focus the flower(s).
Notes: The circular polarizing filter will allow you to dial down reflections while the diffusion filter will soften the edges of the flower petals. Order a diffusion filter in the same diameter as the lens to which it will be attached. Find the diameter on the back of the lens cap that fits the lens.