The most beautiful reefs in the world are located off the coast of Australia and in the Caribbean. They offer wonderful experiences for those to explore. You can either scuba, snorkel or view the reefs from a boat. There are many well equipped tour companies that will cater to people who wish to see the reefs up close. They will either require you to have prior scuba experience or will include scuba lessons before the trip out to the reef.
Unless you know the areas well, it is best advised to go with a established local tour group that knows the underwater areas of the reef like the backs of their hands. Using a company that does not know the area well enough could end up with a disaster such as a life threatening injury.
Reef exploration will give you that once in a lifetime experience. If you can, try and get some underwater photos of your adventure. Explore, have fun and create memories.