The mangrove tunicate is a mild-looking little creature. It’s a type of sea squirt. It’s only about an inch long, and it feeds by pumping seawater through its body and filtering out the goodies. It’s found in colonies in the roots of mangrove forests around the Gulf of Mexico, the Caribbean, and the Atlantic coast of the United States.

Yet this little critter is a powerful cancer fighter. Researchers have used a compound it produces to create a cancer treatment known as trabectedin. It’s used against several types of cancer—especially those in soft body tissue, such as muscles and fat.

Cancer cells find ways to defeat many types of medication. The cells repair themselves, then continue growing and dividing, forming bigger tumors.

A recent study looked at how trabectedin fights cancer. Researchers discovered that the medication “breaks” the DNA inside cancer cells. Although the cells can fix some types of breaks, these appear to be unfixable—the cancer can’t overcome the disruption. That kills the cancer cells and slows or halts their spread.

Sea squirts are surprisingly close genetic relatives to people. And they’re easy to handle and study, so they’re popular lab subjects. So scientists have used sea squirts to create other medications, including cancer treatments. One produced from a different species is used to fight skin cancer, for example. So these quiet little creatures may yield even more treatment options in the decades ahead.

Marine scientists can’t be everywhere at once. To really understand what’s happening below the waves, though, they need a lot of observations—from many places at many times. So they’re getting help from recreational divers. The divers can carry instruments, or just log what they see.

One project is set to begin in December. Known as BlueDot, it’ll provide insights into how the Mediterranean Sea is warming up—not only at the surface, but down to more than a hundred feet.

Many divers wear small computers on their wrists. The computer records location, depth, temperature, and more. Divers who undergo special training can upload those observations to a central database. Scientists then analyze the results, producing a much better picture of the changing sea.

Another project has been around since 2010—the Great Goliath Grouper Count. Divers at artificial reefs off the coast of Florida log details about the goliath grouper.

It’s one of the largest species of bony fish—up to eight feet long and 800 pounds. But the grouper was overfished, so its population plunged. It’s been protected since 1990, so the numbers have gone up. But the extent of the recovery is still unclear.

Volunteer divers keep an eye out for the grouper during the first half of June. They report where they see the fish, the depth, the size of the fish, and more. That helps biologists determine the goliath grouper population—even if they can’t be everywhere at once.

Hotter oceans are bad for just about everyone. They can destroy coral reefs, cause fish to move to new ranges, and rev up monster hurricanes.

There are problems for octopuses as well. Adults of some species aren’t getting as big as they used to, for example. And a recent study found that the still warmer waters we’ll see in the future could cloud their vision. That would make it harder to catch a meal or get away from predators.

Researchers studied the southern keeled octopus, which is found in shallow waters around Australia. It’s a small octopus that burrows into the sand during the day, then comes out at night to hunt.

The scientists placed females in tanks at three different temperatures: a control temperature of 66 degrees Fahrenheit; the modern summer temperature of 72 degrees; and 77 degrees, which is the projected summer temperature for the end of the century.

Almost all the eggs laid in the two cooler tanks hatched. But two of the three mothers in the warmest tank died while tending their broods, so none of the eggs hatched. The mother of the third brood survived, but less than half of her eggs hatched.

Scientists also studied proteins in the octopus embryos that are important for vision. They keep the lenses clear, and they produce pigments that capture light. The study showed that the warmer the water, the less effective the proteins were. So octopuses that hatch in a hotter ocean might need glasses to find their way.