The bob of a simple pendulum is a spherical hollow ball filled with water. A plugged hole near the bottom of the oscillation bob gets suddenly unplugged. During observation, till water is coming out, the time period of oscillation would:

The time period of a simple pendulum is $T=2\pi \sqrt{L/g}$, where $L$ is the distance from the point of suspension to the Centre of Mass (CM) of the bob.When water starts leaking, the CM of the bob moves downwards as the water level drops. This increases $L$, and thus $T$ increases.When the bob is almost empty, the CM moves back upwards towards the center of the hollow sphere. This decreases $L$, and thus $T$ decreases back to the original value.