Scuba diving in the dark is always an adrenaline rush because you know that there are sharks near you but you can’t see them until they suddenly appear. We love night dives because they add an entirely new dimension to exploring the underwater world. We photographed these great hammerhead sharks around Bimini Island in the Bahamas.
Sharks are very comfortable swimming in the water at night. To simplify, their eyes are designed to allow light to pass through the retina twice which enables sharks to see in the dark. It is believed that sharks can see about ten times greater than humans in clear water.
They also have a cephalofoil (the hammer) that is full of electrical sensors. These electroreceptors are interconnected jelly-filled pores called ampullae of Lorenzini and aid in hunting as these sensors pick up electrical signals given off by all living creatures including humans. Therefore, a shark at night is very aware of your presence and location in the ocean even though you have no idea where they are.
When most people think of sharks, they think of species like the great white shark, tiger shark, and bull shark. These are known as requiem sharks and have that classic shark appearance. However, there a numerous species of shark that look very different from requiem sharks including the nurse shark (Ginglymostoma cirratum). These are very common sharks in the Caribbean and often encountered by new divers.
The head is broad with tiny eyes and has two barbels (whisker-like appendages) that are used in the search of food. Their teeth are small and designed for crushing as part of their diet includes eating shrimp, crab, and lobster. They are nocturnal and during the day they are often seen laying under ledges but are also seen in the open on the sand.
They are a fairly large shark and can reach over 3 meters or about 10 feet although most are much smaller. They can tip the scales between 90 to 115 kg (200-250 pounds). The gestation period for nurse sharks is about 6 months and generally, they have between 20-30 pups.
Although many divers see them as harmless, their mouth can produce a tremendous suction and could easily suck in fingers or a hand which they generally will not let go of. Therefore, like all sharks, they must never be touched and need to be respected.
Although we love to photograph all sharks, our favorite is the great hammerhead (Sphyrna mokarran). Generally, it is a cautious shark and will keep its distance from scuba divers. There are 9 species of hammerhead sharks worldwide but the great hammerhead is the largest. An average adult reaches lengths of about 3.6 to 4.3 meters (12-14 feet) but can reach 6 meters (20 feet) and exceed 550kg (1,200 pounds).
Great hammerheads are newer sharks on the evolutionary scale and have developed some unusual characteristics. The unique feature of this shark is obviously the head. The “hammer” which is called a cephalofoil is full of electrical sensors. These pores called ampullae of Lorenzini aid in hunting as these sensors pick up electrical signals given off by all living creatures including humans.
As you view these photographs notice how different the shark can look depending on the angle of the photograph. On a larger shark, the cephalofoil is about a meter (3 feet) in length and the eyes are at the ends which gives it a large range of vision.
The diet of this shark is diverse. They will feed on a variety of fishes including tarpons, porcupine fish and even other sharks. As well, lobster, squid, and octopus form part of their diet. However, their favorite food is rays. Stingrays bury themselves in the sand and the great hammerhead uses its cephalofoil with its electrical sensors to detect their location.
We were looking for the spiny softshell turtle (Apalone spinifera), a native species, in the rivers around Las Vegas. Got some tips from a few local people on where we might find them and after 3 days of searching, we found this unusual turtle. Not sure we would find them as the temperatures had been near freezing which is often when turtles brumate (a type of hibernation for reptiles).
The turtle has an unusual tube-like protruding nose which makes it different from any other turtle we have photographed. It has a thin body and the shell (carapace) is somewhat flexible. Near the head, on the edge of the shell, there are some small spines and hence the name spiny softshell turtle.
We discovered them on some rocks on the far side of a fast-moving river. They were larger than we anticipated. The shell averages 40 cm (15 inches) but can be much larger, especially in females. Apparently, they can live for about 50 years.
At about 10 years of age, these turtles will begin to mate. This occurs mid to late spring as the temperatures warm. On average, the female deposits about 20 eggs on the sunny banks of the river generally in a sandy area or a gravel bed.
Like many turtles, they consume a wide variety of food. Insects and various types of vegetation make up a large portion of their diet as well as fish. They will often bury themselves in the river bottom and wait for a fish to pass by and then ambush their prey.
Our first liveaboard experience was to Guadalupe Island off Mexico in the Pacific Ocean. The sea conditions were rough with waves 7-9 feet and many people were very seasick. The good news is that we handled the conditions quite well and just felt a bit nauseated. It proved to us that we could handle very adverse sea conditions. The 400 km (250 mile) trip started from Ensenada, Mexico and took about 24 hours to cross on the 33 meter (110 foot) vessel called the Sea Escape. Guadalupe Island is a volcanic island and home to some very large great white sharks (Carcharodon carcharias).
The great white shark, also called the white shark, can grow extremely large with some females capable of reaching 6+ meters (20 feet). As the females mature their girth increases considerably for every foot of growth. It was hard to imagine a 1900 kg (4,000 pounds) great white shark swimming a meter or two away from us and we had big expectations. Sadly, the largest shark we experienced was about 4 meters (12-13 feet). Certainly, not a monster female but a very large shark none the less.
Our first experience with great white sharks was in South Africa but the water was not very clear (green water) so it was difficult to get good pictures. As our photographs show, Guadalupe is a great place to photograph these majestic creatures. We will certainly do Guadalupe island again with hopes of photographing a massive female.
Our previous posts on the Revillagigedo Archipelago, also called the Socorro islands, have included the giant mantas(Manta birostris), whitetip reef sharks(Triaenodon obesus), and silky sharks (Carcharhinus falciformis). Although Galapagos sharks (Carcharhinus galapagensis) are fairly common especially at Roca Partida, we did not have any encounters with them there. However, on one dive we did come across a few juveniles at Socorro island and this gave us an opportunity to photograph this species.
Older sharks of all species have very scarred bodies which are simply a result of surviving in a dangerous ocean environment. However, these juvenile Galapagos sharks, which were about a meter (2-3 feet) in length, had skin with very few blemishes. Adult Galapagos sharks can reach 3 meters (9-10 feet) in length.