Batu Bolong is a tiny rocky islet located in the centre of the main passage between Tatawa and Komodo Island. The current can flow through this passage at more than 3 knots, and the site is extremely affected by the current. Batu Bolong is best dived at slack, when the conditions are easiest. It is possible to dive the lee of the island when the currents are running, but this should be approached with caution and an experienced guide, as strong down currents can occur. The northern side of the rock is a wall that descends directly to more than 40m. To the east lie some large pinnacles, separated from the main seamount in 20-30 m of water. The southern side is a steep slope, covered in encrusting and tabulate corals.The site is excellent for both divers and snorkelers, and the shallows are filled with the intense colours of corals and fish life. Swarms of anthias, moon wrasse, butterfly fish and sergeant majors obscure the reef. Descending into the clear blue waters, you can’t help but notice that every inch of this site is covered with life. Most of the coral formations are stunted, due to the high currents, but some immense table corals do manage to cling to the rock in some sheltered spots. Spotted and oriental sweetlipscongregate around the table corals, waiting to be cleaned, while large groupers cautiously patrol back and forward. Angelfish and parrotfish graze in the coral gardens, and a plethora of moray eels peer out from their caves. Get up close to the reef (but watch your fins!) as small critters are everywhere: coral shrimps, crabs and nudibranchs abound. In deeper water and out in the blue, many large fish are drawn to this current swept seamount. Sharks, large Napoleon wrasse, giant trevally, fusiliers and surgeonfish are common. Occasionally manta rays, dogtooth tuna, and large schools of rainbow runners visit the site. Watch out for the large whitetip reef sharks that are often found patrolling the pinnacles or resting under table corals. Two very interesting animal behaviours can be observed on this site. In the shallows, sergeant majors lay their eggs on the bare rock and guard them vigilantly. Disturbed by passing divers, the sergeant majors retreat, and hundreds of moon wrasse take advantage of the opportunity to feed on the eggs in a swirling mass of blue-green bodies! Other, smaller wrasse can often be seen spawning. In schools, they swim to-and-fro, occasionally forming a tight pack of 50 or more individuals. Together, this huge mass of fish gradually picks up speed before rising up into the water column in a final, frenetic rush to disperse their eggs and sperm together in a white cloud, to be carried away by the currents.
The hawksbill sea turtle (Eretmochelys imbricata) is a critically endangered sea turtle belonging to the family Cheloniidae. It is the only extant species in the genus Eretmochelys. The species has a worldwide distribution, with Atlantic and Pacific subspecies. E. i. imbricata is the Atlantic subspecies, while E. i. bissa is found in the Indo-Pacific region. The hawksbill's appearance is similar to that of other marine turtles. It has a generally flattened body shape, a protective carapace, and flipper-like arms, adapted for swimming in the open ocean. E. imbricata is easily distinguished from other sea turtles by its sharp, curving beak with prominent tomium, and the saw-like appearance of its shell margins. Hawksbill shells slightly change colors, depending on water temperature. While this turtle lives part of its life in the open ocean, it spends more time in shallow lagoons and coral reefs. Human fishing practices threaten E. imbricata populations with extinction. The World Conservation Union classifies the hawksbill as critically endangered. Hawksbill shells were the primary source of tortoiseshell material used for decorative purposes. The Convention on International Trade in Endangered Species outlaws the capture and trade of hawksbill sea turtles and products derived from them.
Bleaching occurs when corals expel their symbiotic zooxanthellae - pigmented, algae-like protozoa that live within the coral's cells. High temperature, pollution or other stresses can cause the coral to expel its zooxanthellae, leading to a lighter or complete loss of color.