Manzanillo beach is located near the northern tip of Margarita island, not far from Playa El Agua. You will find it soon simply following the main road from Playa El Agua. It is a small beach, not crowded at all.
Since Manzanillo is actually a small fishing village, you might see a fleet of fishing boats in the bay, or even catch the scene of fishers drawing their nets to shore.
The bay is protected so waves are not nearly as bad for swimming as at Playa El Agua. There are several restaurants that will rent beach chairs and umbrellas, plus serve food and drinks.