Snorkeling Malmok Beach is popular especially with Aruba's boat tour companies. There are two small coves in the iron-shore with mostly sandy beaches where you can enter the water without taking a boat tour. If you want to avoid the crowds and noise when the tour boats are here, go early in the morning.
But in our opinion the other spots on this northern part of the island have much better snorkeling. Though we did see many schools of fish, and there are some rocks along shore to see a few sponges and feather duster worms, the rest of the area is a sandy bottom with some seaweed.
For snorkeling Malmok Beach you can choose which of the two small sandy beaches you like for your entry. You can enter without shoes, but watch for any rocks sticking up out of the sand.
The area of the most interest snorkeling Malmok Beach is the rocky shoreline. We found the life on the rocks to the right better than to the left, but since you're here check them both out. There are boulders with some growth on them of sponges and feather duster worms, and fish around them. Swimming just a little farther out from shore, over the sandy bottom, there are a few scattered tube sponges. In this area you might also encounter some schools of aggressive fish. They are used to being fed by the tour boats. The depths are about 10 feet through the whole area.
Unfortunately we had terrible visibility. There was an algae bloom and it was floating in the water and stuck to all the surfaces. Hopefully this is not the case during your visit.
There were schools of fish and some other creatures to see here.
Caribbean Fishes ID eBook