Two sediments resulting from swimming pool operation are characterized and the data discussed, namely the flocs which accumulated and were backwashed from deep bed filter, and bottom sediment collected from the pool by vacuum cleaner. Better understanding of sediments' structure and properties should allow for improvement of Cryptosporidium oocysts removal from pool water and as a consequence - increase the safety of pool users. Zeta potential, nano-size and micro-size of particles/flocs and derivatographic measurements were performed. The zeta potential data indicated easy flocculation and size distribution measurements revealed varied effectiveness of deep bed filtration. Derivatographic analysis indicated differences between sediments from filters backwashing and pool bottom sediments.