There are many dive sites and moorings around Lady Elliot Island. Their locations are difficult to find without a quality map. Here is a comprehensive list of the dive sites around Lady Elliot Island roughly in order of popularity.
Lighthouse Bommies
The lighthouse bommies on the western side of the island is the most well known location on the island. It's an ideal place to find all manner of marine life. It is the place where you have the highest chance of encountering manta rays. Manta rays commonly use the bommies as cleaning stations. Lighthouse is easily the highest rated location on the island. The lighthouse quayway is also one of only two entrances on the western side.
Forty Five
Forty Five is the No Anchor mooring placed at a forty five degree angle to the south west of the Lighthouse Bommies. It's a single lone bommie that presents more opportunities for manta rays.
Lagoon
The lagoon on the eastern side of the island is incredible spot. It is tidal dependent. That means you can only swim in there at high tide but it also means that it is very shallow and that makes it ideal for beginning snorkellers. The lagoon, especially in the vicinity of Channel One is full of friendly sea turtles. The lagoon is full of all kinds of sea life. It's a great place to see the Great Barrier Reef close up.
Coral Gardens
The Coral Gardens quayway is the second entrance on the western side. The area around coral gardens has some of the prettiest coral structures on the island with large swim-throughs, archways and large corals. Some of the best dolphin interactions happen in the area around Coral Gardens. I have even swam with a fur seal here.
Spiders Ledge
This is just about as far north as the boats will ever go. Spiders Ledge is spectacular. The ledge is a large dropoff with some of the most incredible coral cover on the entire island. It also backs onto some of the deepest water on the island and that means that animals of any size might make their way through the area. Usually also has some of the clearest visibility on the island. This spot is just about impossible to get to without a boat.
Simmos
This mooring sits on the big sandy patch on the western side of the island. There's always something interesting on the sand. It's not uncommon to find stingrays, turtles and eagle rays swimming around in this area. During manta season, you often get mantas cruising on the surface. My favourite snorkel path on the island takes me between here, Lighthouse bommies and the lighthouse quayway.
Second Reef
Second Reef is particularly special. It's the enclosing shoulder of the great sandy patch on the western side of the island. The reef through here starts very shallow and gradually deepens and heads towards the Lighthouse Bommies. Beyond the reef here, the bottom falls off more rapidly and so you can often encounter large animals coming in close.
Sunset Drift
Just about as far south as the boats will take you. Sunset Drift has amazing coral as well. The area between here and the lighthouse bommies is a great place to find manta rays feeding when in season. Unfortunately the currents here make it exceptionally difficult to get here without a boat. Humpback whales also use this area to go around the island.
Encounters
While not being marked precisely, encounters is the area beyond the reef edge at the southern end of the airstrip. This area is excellent for encountering manta rays on the surface when the season is right and can provide a decent snorkelling experience during northerly winds.
Blowhole
The blowhole is an interesting cave structure on the eastern side of the island. It's inaccessible most of the time because it's on the windward side of the island and even then is too deep to snorkel. The cave is a great place to sit inside of while diving. You can watch silvertip sharks get cleaned outside. The blowhole is a great starting location for a dive along the eastern wall.
The Severance
The shipwreck on the western side of the island is a favourite of all the guests that get to visit it. The buoy that marks it is the furthest one west from the beach. Visibility can be hit and miss through this area but when it's good, it's really good.
Three Pyramids
Named for the three bommies lined up in a row in decreasing size. These bommies are full of interesting creatures, from little shrimp to rays and sharks. It's position is very close to The Severance so many dives move between here and there. It's always great to look out into the deeper water here because you never know what might come out of the blue.
Maori Wrasse Bommie
Maori Wrasse is an interesting little spot. It's just a little wider and further north than Coral Gardens. You can plenty of different types of animals through here with turtles being common.
Turtle Beds
Turtles Beds is at the southern end of the first snorkel line. It's named for the large beds of coral that have been hollowed out by turtles resting in them. Turtles are very common in this area.
Mooring One
Primarily a boat mooring but definitely worth mentioning because of it's proximity to the Lighthouse quayway and the Lighthouse Bommies. This mooring sits at the entrance to the great sandy patch. It's quite common to find squid hiding underneath the boat that is moored here.
Devils Marbles
This position is now marked by the southern public mooring on the island. The bright blue buoy sits over the position of a series of bommies on the bottom that are a great place to find manta rays. In whale season, it's very possible for whales to make their way through this area.
Nemo Wall
The Nemo Wall is part of the drop off from the reef flat. If you swim north from the Lighthouse Quayway along the wall, you'll find a whole heap of anemonefish and anemones in front of the Private Boatshed. It's one of the easiest places to find nemos on the island
Shark Pool
Everyone is always asking about the Shark Pool. It's a little difficult to get to, being past the northern end of Coral Gardens. During the summer months the chance of finding sharks in this area is particularly high. Sometimes you can be swimming with a dozen whalers.
Chain Bommies
These bommies are named for the large chain that is wrapped around them. A long forgotten relic of a ship than ran foul on the reef. These bommies always remind me of Three Pyramids in terms of the marine life and the general feel of the area.
Sandy Seconds
Commonly confused with the unnamed "Great Sandy Patch" on the western side. Sandy Seconds is the location in between the two snorkel lines. This area is a great place for beginner divers because of it's sandy bottom and proximity to second reef which makes for a nice easy dive. After rainfall, this area does cop a heavy amount of runoff from the island and so visibility can drop to relatively low levels.
Reefy Seconds
This location is on the other end of the snorkel line. It's the southernmost buoy that's attached to a snorkel rope. The area south of this spot gets hit hard when swells are large so there is often a lot of coral rubble and storm debris in the area.
Anchor Bommie
This bommie is known for the large anchor that sits in the sand nearby. There are many anchors scattered around the island in various locations. Anchor bommie sits at a similar depth to Three Pyramids and offers similar wildlife interactions to that area. It's definitely possible to spot manta rays in the area as well.
Hiros Cave
Hiros cave on the eastern side of the island is a lot smaller than the Blowhole and arguably less interesting. The eastern wall along here is spectacular though with sea fans and soft corals that you don't really get to see in numbers anywhere else.
Tubes
Tubes is a location that sits in between the Blowhole and Hiros Cave. The entire wall along here is very interesting and offers much the same sort of experience as the Blowhole and Hiros. Up above the lip of the wall is a series of spur and grooves that enclose the entire eastern side of the island. These structures are built by the motion of water.
Groupers Grovel
This location is rarely visited these days. It's very similar to the structures and marine life you'd find at the Blowhole, Tubes and Hiros; albeit with a slightly shallow incline. Groupers are commonly found hiding in the grooves that form the eastern ring of the island.
Jems
This reef sits well out to see and was discovered via aerial photography. It's secrets remain highly unknown as nobody in modern times has dived or snorkelled it. It sits an extraordinarily long way out from the island and is therefore unsuitable for regular operations.
Inside
This boat mooring sits on the reef flat, just a little north of the Lighthouse Quayway. It's earned a place at the bottom of this list purely because it's regularly mistaken for a turtle taking breath. Funnily enough, there are plenty of turtles that frequent the area at hightide.