In the interest of protecting and improving the quality of the environment and protecting people's health, Croatia adopted the The Bathing Water Directive in 2009. Due to changes in science and the technologies, a revision of Directive 2006/EC was proposed in 2021. According to the regulations from 2006, the rating of bathing water quality is determined by calculating percentiles using the arithmetic mean and standard deviation. This assumes a log-normal distribution of microbiological parameters, which is not always achieved. Earlier research showed that the non-parametric Hazen method proved to be more suitable for calculating percentiles. This method is already applied in some countries, such as Australia and New Zealand. The aim of this work was to compare whether there is a statistically significant difference in the bathing water quality obtained by calculating percentiles using the parametric and Hazen method. Data on the microbiological quality of the bathing water were collected on 317 coastal locations of the Primorje-Gorski Kotar County, in the period from 2009 to 2022. The results show a significant but small difference effect. The biggest contribution to the difference between the methods is the change in quality from "Excellent" to "Good" and in the case of E. coli to "Satisfactory". Furthermore, E. coli manifest significant changes from "Satisfactory" to "Good" and "Unsatisfactory" rate. The Hazen method gives higher median values, there is a greater dispersion of data and more extreme values are achieved. More changes are visible in the direction of deterioration when using the Hazen method. Since the Directive's main objective is to protect human health, it would be more appropriate to use the robust and conservative Hazen method.