This is a formula how to calculate your own waterfall collared top or sweater. Any yarn with good draping quality is suitable (some examples are given in the recommended yarns list but in general you can consider rayon, linen, cotton, wool or blends thereof). You have to take one measurement and to calculate your gauge, then to do some easy arithmetics. The top (or sweater, if you choose to make sleeves) is seamless and worked top dowun. Thus, you can try on as you go. For a sleeveless top, you would approximately need between 440 m (S) and 600 m (XL).
I’ve knitted several from different yarns with different collar sizes. You can buy the formula on Ravelry and see many tops from different yarns.