We recommend snorkeling the Antilla wreck. The sunken World War II ship is offshore near the north end of Aruba. There is enough of the wreck visible from the surface for snorkelers and there is a good amount of fish to see too. Just know that choppy water and wind are common out at the wreck and there is normally a current you must swim against, so don't expect it to be flat water.
The Antilla Wreck is 400 feet long, with the front third or so of the boat in shallow enough water to be enjoyed by a snorkeler. It is laying tilted over on the bottom, in about 60 feet of water. The visibility was decent when we were there, but not great. The top masts are closest to the surface, reaching to within about 5 feet of it. In fact, all the boats have chains attached to these areas of the wreck for their mooring pins.
Besides the masts, the bow and a portion of the forward deck are fairly visible while snorkeling the Antilla Wreck. These areas are covered in small corals and lots of colorful sponges. And there are many fish, with a few species that you don't normally see snorkeling in Aruba, and some that are much bigger than you see shore snorkeling.
Snorkeling the Antilla Wreck is only accessible by booking a boat tour. We wondered if you could swim to it from Malmok Beach; it doesn't look that far offshore on the satellite maps. But don't try to swim it. It's too far, there are strong currents and the water is rough too. Not to mention all the boats coming and going.
Lots of different companies do boat tours to the Antilla. They most often leave from Palm Beach in front of the high rise hotels. You can go on a sailboat or motor boat. All boats in Aruba serve alcohol, but some are more party oriented than others. A tour to the Antilla is commonly combined with snorkeling another spot, usually Catalina Cove or Malmok.
Fish hang around the wreck and it is becoming encrusted with some corals and sponges. In addition to the fish listed below we also saw big schools of silversides.