The bob of a simple pendulum executes simple harmonic motion in water with a period $t$, while the period of oscillation of the bob is $t _ { 0 }$ in air. Neglecting frictional force of water and given that the density of the bob is $\left( \frac { 4 } { 3 } \right) \times 1000 \mathrm {~kg} / \mathrm { m } ^ { 3 }$. What relationship between $t$ and $t _ { 0 }$ is true?\\
(1) $t = t _ { 0 }$\\
(2) $t = t _ { 0 } / 2$\\
(3) $t = 2 t _ { 0 }$\\
(4) $t = 4 t _ { 0 }$