Weird and wonderful things about the ocean

Tiny organisms called bioluminescent plankton can make our seas sparkle electric blue at night. Sometimes our beaches look like liquid starlight when the surf moves. This usually happens during a red tide. If the water turns rusty brown, bioluminescence might happen that night. 

How do you know if there’s a red tide? There is no dedicated site to check for red tide conditions. Most locals use beach cams (such as Muizenberg) or refer to social media for updates (such as the Cape Town Bioluminescence Facebook group).

This is possibly one of the weirdest fish in the ocean – the barreleye fish. It does indeed have barrel-shaped eyes. It also has a transparent dome-like head. To make it even weirder, its eyes are inside this transparent skull, and they glow. You can actually see its glowing eyes swivelling about in its head.

Sometimes the eyes swivel up (unusual for fish), and scientists reckon that this is so they can see their jellyfish prey above them in the dark. You are not likely to spot these at Clifton beach, though - they live in the ocean's twilight zone, roughly 600 to 800 meters below the surface.

The best way to see this weird fish is in this video.

This animal’s clicks are so powerful they can reach 230 decibels underwater (equivalent to 170dB in the air)— louder than a jet engine - loud enough to pop your eardrum.

And what animal makes these loud clicks? The largest of all toothed predators – the sperm whale! Capable of holding their breath for up to two hours, they are clearly superior in many aspects. And guess what? They also have the largest brain on the planet. At about eight litres in volume, it’s about five times as large as a human brain.

The secret to ageing? According to the Immortal Jellyfish, the trick to this is to collapse into a polyp. The Immortal Jellyfish is a tiny jellyfish, smaller than your nail, that can revert to its juvenile form instead of dying. When stressed, injured, or ageing, this tiny jellyfish reverses its life cycle! Of course, if it gets eaten, it’s going to die.

Imagine a snail. Now make it bumpy, pink and have huge eyes. Oh, and make it a fish. You have just described a newly discovered “bumpy snail-fish”! It lives more than 3,000 metres below the surface off the coast of California. Researchers found it using remotely operated robots – so it’s unlikely you are going to see it when swimming in Fish Hoek. But you now know that this cutie exists!

Did you know that the star of the Octopus Teacher (the non-human star) has blue blood? And that each of the octopus’s arms has a mind of its own? Yes, the octopus has THREE hearts and eight brains. All those brains make it a very special invertebrate (animal without a spine) as it’s the only one to pick up tools and use them (some octopus species collect and carry coconut shells, using them as portable shelters).

You can find these amazing sea creatures in Cape Town! Look carefully for their suckered tentacles tucked in rock crevices at low tide in rock pools and Cape Town tidal pools, like Dalesbrook Tidal Pool. 

South Africans will know the famous slogan – “It’s not inside, it’s on top.” Did you know there are ocean waves that are not on the surface but inside the ocean? No surfer is going to be able to ride these waves!  

Internal waves move beneath the ocean surface between layers of different water temperatures and salinities. They can be taller than skyscrapers and tens to hundreds of kilometres long! However, because they are underwater, we cannot see or feel them; They are only visible on satellite images. They do not affect the sea’s surface or boats, but the idea of a huge wave beneath the sea’s surface is bound to make some butterflies flutter in the stomach!

Since 2011, during springtime, up to 200 humpback whales gather in ‘superpods’ off the west coast of South Africa. It is historically rare for humpbacks to gather in such numbers. Scientists attribute these gatherings to two main factors: rapid population recovery following the ban on commercial whaling, and highly concentrated food sources. These groups may also serve as large social and learning events, allowing younger whales to learn collective feeding tactics such as "bubble-netting".

Not only do the South African waters support huge pods of humpback whales, but all the little bays and coves, including False Bay, off our Cape coast, provide sanctuary for calving Southern Right whale mums. Whale mothers give birth every 3 to 4 years, after a gestation of about 1 year. The calves are roughly 5 meters at birth, and nurse for several months in sheltered bays before accompanying their mothers to feeding grounds in the icy Antarctic. Newborn calves lack the thick blubber layer needed to survive in the freezing, rough waters of Antarctica. So the mothers choose our (relatively) warmer and calmer waters as their birthing pools! 

You can easily spot Southern Right whales from the shoreline at Hermanus (they come that close) or along the False Bay catwalk or Fish Hoek beach catwalk.

Cape Town’s seas contain a special type of forest - giant kelp forests. Formed by long stalks of giant kelp, some of which can grow over 10 metres tall, these forests provide shelter and food for a kaleidoscope of sealife, from tiny crustaceans to large fish, and are among the most productive ecosystems on Earth. The giant kelp can grow as fast as 30-50cm a day, which means that it can regrow quickly after storm damage or in response to nutrient pulses. This is a forest which sways with the surge of the sea, hides seals in its fronds and has anemones ‘flowering’ at its base.

SEE: Cape Town’s underwater wonder makes cover of TIME magazine

If you want to swim amongst the kelp, a good place to start is snorkelling at Windmill Beach (Simon’s Town) or Miller’s Point, where there is dense kelp near the tidal pool.

Sunfish are the gentle giants of the ocean, holding the title for the world’s heaviest bony fish. As their name suggests, they look rather like a large, round sun drifting near the surface of the sea. Weighing up to 1000 kg, all of which is sustained by mostly jellyfish, these fish are often seen off our coast in the warm summer months. Kayakers and freedivers often spot sunfish just offshore from Sea Point and Clifton.

It is incredible how many of the sea’s wonders can be found right here off the Cape Town coast. Take some time on World Ocean Day to celebrate just how lucky we are with our city of mountains and sea.