Achieving neutral buoyancy is an essential coral reef diving skill.
The modern buoyancy compensator makes such skills relatively easy with a bit of practice. All it takes is knowing exactly (not approximately) how much weight you need to make you slightly negatively buoyant, and then learning to add/remove air in very small doses until the desired effect (neutral buoyancy) is achieved at any depth.
Remember, the amount of weight a diver needs to be slightly negatively buoyant at the surface will change with a number of factors, including weight of the equipment you carry, changes in your own body weight, and the water density at your dive site.
The density of tropical seas in which coral reefs thrive will almost certainly differ from that of the water in your local pool or lake back home, so a bit of on-site fine tuning of the proper weight to carry will usually be necessary upon arrival at your coral reef diving destination. This is best accomplished by making your first dive in the calm shallow waters of the lagoon (back reef zone) where you can fine tune the amount of weight you will carry without dealing with waves, currents, and other distractions.
If you need help in mastering neutral buoyancy, don’t hesitate to ask your dive master or other advanced divers in your group.