Abstract: An analyzing system for analyzing fluid samples includes a measuring buoy immersible in a body of fluid to be tested. The buoy forms a sample chamber in which samples of the fluid are to be tested. The sample chamber communicates with a settling chamber through a chamber opening, and the settling chamber communicates with the body of fluid through a floor opening formed in the buoy below the chamber opening. A gas exchange apparatus communicates with the sample chamber and with a source of air or gas for introducing the air or gas into the sample chamber to drain sample fluid therefrom, and for discharging the air or gas from the sample chamber to admit sample fluid into the sample chamber from the settling chamber. A testing device is disposed in the sample chamber for testing the sample fluid, and is connected to a control and analysis device.