Fig. 6. Vertical frequency distribution of observed drift rates (left), and curves representing the predicted drift rates (assuming no residual air) of a seal with a total body volume of 100 litres (right). The three curves correspond to the predicted drift rates using published drag coefficients (C_D) for a cylinder (red dashed line) and a sphere (solid black line) from Vogel, 1981, as well as for a harbour seal (blue dotted line) from Williams and Kooyman, 1985. The horizontal dashed lines represent the maximum kernel density for all observed positive and negative drift rates separately, while the dotted lines represent the range of the 95% probability of occurrence (kernel density function, bandwidth = 2 cm s^-1).