Coral Cove is a Fortnite landmark, which means it doesn't appear on the map, and you'll need to be in the area before the name appears in the corner of your screen. You can find Coral Cove northwest of the main island, near Sweaty Sands.
The area, mostly in the middle of the sea, is pretty sparse when it comes to looting, but it's close enough to Sweaty Sands to make it a reasonable place to drop off. You can also drive from Coral Cove to the nearby Giant Whirlpool and easily get to Pleasant Park if you need to.
The main reason people will want to find Coral Cove in Chapter 2 of Season 3 is part of the Aquaman challenges, as you have to find three Tridents there for one of the quest stages.
The Tridents can be found in Coral Cove, which you can find northwest of Sweaty Sands. There are three in total. One is located southeast of Coral Cove, the second is northwest of Coral Cove, and the last is located directly north of Coral Cove.
All three can be found on rocks protruding from the sea and are fairly easy to find. All you need to do is interact with the Trident to claim it, then move on to the next one.
The area will be quite busy, as everyone will be trying to get their skin on, and you will also have to watch out for sharks, which are quite common in the area and very aggressive.