Did you know the ocean covers around 70% of the Earth? That’s a lot of water to explore. And when you dive deeper, you’ll discover plenty of ocean mysteries to make you say “Whoa!” You may have heard of unexplained disappearances in the Bermuda Triangle, the strange deep-sea sound called the Bloop or the mysterious Yonaguni Monument, but here we’re taking a closer look at ocean mysteries that are threatening the health of our blue planet.
Scientists around the world are trying to solve these mysteries because they aren’t just campfire stories — they are conservation emergencies. Finding the answers will help preserve the ocean for the future, for us all.
Sunflower Sea Stars Wiped Out
Around a decade ago, sunflower sea stars in the northeastern Pacific began dying in vast numbers. This phenomenon became known as Sea Star Wasting Disease (SSWD), but the exact drivers behind the die-off remain unknown. In the delicate ecosystem, this sudden change had several knock-on effects.
The ecological impact was immediate. A decrease in the number of sunflower sea stars meant that the population of purple sea urchins, the favored prey of the sunflower sea star, exploded. These urchins are now devastating kelp forests.
Kelp forests are vital for marine biodiversity and carbon capture. They’re also spectacular dive sites, offering cold-water divers a magical world to explore. The key to rebalancing these ecosystems is to understand and ultimately solve the ocean mystery of the disease.
There is hope. In August 2025, researchers in Washington State made a breakthrough discovery and identified the virus that causes the disease. The next step is investigating how sea stars could build resilience against this disease. In the meantime, the diving community is actively removing sea urchins to give kelp forests a chance to regenerate.
The Case of the Disappearing Plankton
Every drop of ocean water contains thousands of plankton. These microscopic organisms form the foundation of the world’s food web and produce roughly half of the oxygen we breathe. They are essential to life on Earth.
Scientists have shown that climate change and rising ocean temperatures are upsetting their balance. What remains uncertain is what impact these shifts may have.
Interpreting the data is complex, making firm conclusions difficult. Some long-term studies suggest 50% of the phytoplankton biomass may have been lost globally since the 1950s, with ongoing declines estimated at 1–2% per year. Other research indicates that in some regions the number and diversity of plankton are actually increasing. While the future of plankton looks good for some species and bad for others, what is clear is that the picture is constantly changing. For now, plankton remain an ocean mystery that will likely continue for decades to come.
Mysterious Whale and Dolphin Strandings
It is a sad reality that marine mammals become stranded. They drift into shallow waters and are beached due to natural causes or human impact. Data released in 2025 revealed that the number of whales, dolphins and porpoises stranded in Scotland had risen from around 100 per year to more than 300 over the past three decades.
While the reason for the increase remains unclear, scientists suspect that human activity may be playing a significant role. Potential causes include declining fish stocks, entanglement in fishing nets, plastic or chemical pollution and noise pollution.
This is an ocean mystery that requires urgent attention. Because these mammals sit at the top of the food chain, they serve as indicators of wider environmental pressures. As different regions face unique challenges, scientists have suggested that targeted, region-specific responses are the most effective strategy. In the meantime, divers and the general public can help by reporting mammal strandings to local authorities.
How Can I Get Involved in Ocean Conservation?
Inspired by these ocean mysteries? Activate your inner citizen scientist and gain a specialty certification with PADI AWARE’s Dive Against Debris course, and learn tangible actions to create positive ocean change with the PADI AWARE Specialty Course or AWARE Shark Conservation. You can also help protect marine life by taking the Ocean Pledge to become a PADI Ocean Torchbearer.
