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I have been diving Hawaii since 1985, and, after more than 150 dives there, Lana'i remains one of my favorite dive destinations.
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UNDERWATER TERRAIN
This collection of images conveys some of Lanai's undewater magic: its starkly beautiful lava structures, its large animals and wild pelagics, and some of its fabulous reef fishes.
The Hawai'ian islands are the visible tips of hugh undersea mountions formed by volcanoes whose lava eventually flows down the slopes into the sea. There, as the lava cools and is shaped by the currents, it creates a vast array of underwater tubes, ridges, arches, caverns and other structures that often seem like a surreal underwater world...
Lana'i is a place of "big" landscapes...[This dive site is near Barge Harbor] 
...Of massive arches...like this one near 1st Cathedral
...Smaller ones are often stunning windows on the sea...
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...That you keep finding all over...
...Which only keeps you searching them out.
Inside the caves and tubes, fragile lattice works of lava are often found...
...And, half the fun is that you never know what you'll find...
...They're so beautiful they just keep beckoning you in...
...Sometimes you find...Whimsy...
...But always you go on looking for more...
FANTASTIC REEF FISHES
Lana'i reef fish are colorful (and many are endemic to the islands). Please respect our copyright: If you want to use one or more of these photos on your web site, for wallpaper on your desktop, or on a T-shirt, we ask that you purchase our Green Divers CD ROM: click here for more information. 
At Monolith Rock, an 15-18 ft manta passes over my head in 40 ft of water...luckily I was able to catch up to it from behind, and, because of the angle, was able to get it all in the frame...(but the web just doesn't do it justice!). To read more about what was one of my "best dives," click here, but don't forget to return!)
An eagle ray cruises the "back side" of "Pyramids." They are carnivores (unlike the planton-feeding Mantas), and they often seek out shellfish on the sea floor. When not "flying" through the seas, rays are often motionless on the floor (and sometimes cover themselves with sand). The long tail bears one or more venomous spines.
A white tip reef shark leaves "1st Cathedral"...The white tip is one of the most common sharks found on the Hawai'ian reef, and during the day it often 'rests' in caverns, tubes or under large overhangs. Hunting mostly at night, the white tip feeds on fish and crustaceans. Unless provoked (or its avenue of escape blocked by divers), this shark can be considered harmless...
Here, the presence of the diver and camera stirs a white tip from its daytime resting...once the diver leaves, the shark often returns to the same spot...
At another spot, a third white tip heads away from an encounter with this photographer...
One day, at 105 ft down., this yard-long Jack inspected ME! Also known as "trevallies," about 2 dozen species of jacks are found in Hawaii. The most common is the Bluefin Trevally, which hunts alone or in small groups. Swift, agile predators, they feed on other fishes (but also may be seen on the bottom looking for crustaceans).
...Elsewhere, a school of 50 jacks cruises by...
...And, often other top predators, like this "Great Barracuda," are seen in the distance. The barracuda, like the jack, hunts alone or in small groups, and is often encountered by divers.
Another in-shore visitor often seen by divers is the Green sea turtle, which are not uncommon off Lanai, but are more frequently seen off of Maui.
...They're inspiring, majestic animals
...That you'll find in almost every underwater environment, under ledges, in caverns, or, as here, suddenly cruising up a deep cavern...
Convict Tangs browse the reef in a small gang. Like other surgeonfishes (named for the sharp spines at the base of the tail), and also known as tangs, these fish mostly feed on algae that flourishes in shallow, sunlit waters. It is thought that their preference for rather large schools is a defense mechanism.
Needlefish near the surface, hunting. These fish are carnivores and their prey is often small fish. Although related to flying fish, they cannot "fly" like their cousins (although they can skim the surface or leap out of the water).
Pennantfish by a pinnacle. This butterflyfish may be found along dropoffs, feeding on zooplankton, and are readily identifiable because of their long white pennants (which increase with age).
Bluestripe Snappers lurk in a tube. Introduced into Hawaii from the Marquesas in the 1950s, this fish has become abundant in Hawaii, and is a successful predator (displacing other snappers). Their Tahitian name is "ta'ape."
Racoon Butterflyfish (surround a lone Threadfin). During the day, these nocturnal-feeding schools of algae-eating fish often follow divers around, exhibiting total fearlessness in approaching them.
Peacock Grouper. Another species introduced from French Polynesia in the 1950s, these beautiful groupers are often difficult to photograph.
Orangespine Unicornfish at a Hawaiian Cleaner Wrasse "station." The small irridescent wrasses eat the parasites off of obliging (larger) fish at "stations" all along the reef. The juvenile of the species is a bright blue, while the adult displays a familiar multi-hued coloring.
Yellowfin Surgeonfish. These fish often graze the reef in big schools, seeking out algae. They are aggressive feeders, and often crowd out other algae-feeding fish (because of their large size). They're also friendly and approachable in many locations, readily coming up to divers.
Orangeband Surgeonfish. Another territorial fish, with real aggressive tendancies, that is often found in surgy waters. A brilliantly colored fish, with distinctive markings.
Spotted Pufferfish (with Yellow Tang). The puffer is one of the many species of fish that actually feeds on the coral polyps living "within" the reef (biting it off in its teeth).
Spotted Boxfish. Also known as "trunkfishes," these small unique fish have a polygonal shape, and are slow swimmers (making them rather easy photographic subjects). They are omnivores, feeding on both plants and animals.
Picasso Triggerfish. Hawaii has many species of triggerfishes, which are similar to filefishes, pufferfishes, and boxfishes. They eat a wide variety of things: crustaceans, coral, plankton, etc. The Picasso is very common on shallow reefs, "but is one of the most difficult to approach or photograph."
Moorish Idol. Is closely related to surgeonfishes, and has been called the "classic reef fish" because of its evocative shape and color. (They are unrelated, but very similar to, the Pennantfish.)
A pair of Bandit Angelfish. They feed on sponges, and are frequently encountered in pairs at depths below 100ft.
A rare Longnose Hawkfish (in a black coral tree: look closely!). Because most black coral has been taken by divers in all shallow Hawaiian waters, these fish are often only found at depths greater than 100ft. If you are lucky enough to find a black coral tree at shallower depths, look carefully for the longnose--it may be there!
A Scorpionfish. These fish have venomous spines, and are often camouflaged so that other fish find them difficult to spot. This is the Devil Scorpionfish, which has a hump on its back, and deep depressions on the top of the head and in front of the eye.
Milletseed Butterflyfish (surrounding a Whip Coral). This is the most common species of butterflyfish.
Hawaiian Dascyllus (Damselfish) in an Elkhorn coral head. Damelfishes fall into two categories: some are carnivorous, others are omivorous. These are the former, feeding on shrimp and crab larvae, among other things. Young often hide out in the branches of coral, as these are doing.
Saddleback Butterflyfish. Usually found in pairs, and are not common in Hawaii.
Gilded Triggerfish. Has scales with a small white spot in the center of each one. It is a herbivore.
Oval Butterflyfish. Occur usually in pairs, and feed on coral polyps.
A rare Reticulated Butterflyfish. Not common in Hawaii. Feed on coral, and occasionally on algae, and are also usually found in pairs.
3 Bi-colored Anthias. Yellowish on the upper half; blueish on the lower half. They usually only found in deep waters (at depths below 60ft.). These three are hard to see, in part because they're also a very skittish fish that's difficult to photograph, and I couldn't get any closer to them without scaring them all away...