Cd = 1.5;
Diameter = 0.2032;
densitySW = 1025;
PlatormArea = (pi/4) * diameter^2;

Clinearize = 4.986;

(1.51*10^-3) / (7.78 * 10^-3)
b = 0.5 * SWDensity * Cd * Area * Clinearize;

mass = 38;

H = tf([a],[mass b 0]);

bode(H)