Radium and radon isotopes within the water column can indicate the origin and the movement of water masses. Therefore radium and radon isotopes are regarded as important tracers to study the ventilation and mixture of different water masses in coastal regions. Especially the activity of 226Ra is an important parameter to indicate the groundwater input and the influence of the open ocean. Traditionally, the standard method to detect 226Ra activity is using gamma-ray spectrometer. Kim et al. (2001) and Geibert et al. (2013) came up with new methods to measure the activity of 226Ra. In this project I will discuss the three methods, with a focus on comparing between Geibert’s new methods and gamma counter.