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.
Most divers encounter southern stingrays (Dasyatis americana) buried in the sandy bottom during a dive in the open ocean. During our time on Bimini island in the Bahamas, we decided to snorkel around the shallow mangroves in search of juvenile lemon sharks. Mangroves are critical environments for juvenile fish and sharks because it acts as a nursery for many species. Protected from the predators in the open ocean these shallow waters with their massive root systems provide protection.
We didn’t find any sharks but we were surprised to see so many southern stingrays around the shallow mangroves. There is a relatively large population of great hammerhead sharks that inhabit these waters at this time of year. Because the main predator of these rays is the great hammerhead shark we wondered if they modified their behavior at this time of year to try to avoid these sharks.
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.
Silver Banks in the Dominican Republic is about 50 miles (80 km) northeast of Puerto Plata and is only accessible on a liveaboard. It is one of two places in the world where you can legally get in the water with humpback whales and only about 630 snorkelers are allowed to go each season (January – April). However, in water encounters are restricted to a few situations only that include sleeping whales, singing males or a “Valentine” when the male is courting the female and the two are gently dancing around each other.
The majority of the expedition had no in water encounters as the whales were constantly on the move so it turned into a glorified whale watching trip. However, the above water interactions were numerous and close and included breaches and pectoral slaps. For those who have not experienced humpbacks then these encounters were second to none. Unable to get in the water we resorted to hanging our cameras over the boat and blindly shooting towards the whales hoping to capture them under water. Fortunately, we were able to get some reasonable shots.
A female that has given birth to a calf will generally have males competing for her attention and mating rights. There is an escort, a male that currently has battled off his competitors and swims next to the female and calf. Then there is the challenger, another male that is attempting to replace the escort. Battles between males occur and the winner temporarily becomes the escort until another males challenges. The mother and calf, as well as the escort and challenger, can be seen in this photo.
Unfortunately, it was not until the last day that we came across a mother and a calf that had no accompanying males. The mother can sleep for 25 minutes but the calf needs to come up for air every few minutes. This mother was stationary at about 40 feet and the calf would swim from beside her or under her to the surface, breath and return to her. This was our only good underwater encounter of the week.
Upon reflection, these are wild animals and interactions with them are on their terms. Sometimes they give us only a brief moment to share their world and at other times we get lucky and have numerous and spectacular encounters.
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.