A "tip reef" refers to a small part of a coral reef that extends up to the surface of the water. It is like the tip or the very top portion of the reef that you can see. Full definition
We seem to have a community of white tip reef sharks. (twofishdivers.com)
Carefully looking into the large pools we see white tip reef sharks who are almost dancing around the edge especially for our entertainment. (worldwideadventurers.com)
Below the water you will be surrounded by a world of black tip reef sharks, colorful clown fish, turtles, and loads of macro critters. (DiveAdventuresAsia.com)