Ocean Watch

A while back, I listened to a local author read a passage from his novel about a man's long-distance swim. Something creepy brushes against the guy's skin, but he is neither attacked nor stung. He gets rescued in the nick of time, but the identity of the brusher is never revealed.

"What was it that touched the man?" a woman from the audience asked.

The author shrugged. "I don't know, but it happens to me a lot when I swim at Ala Moana. Something soft touches my skin, but I never see what it is."

Could it be moon jellies, I wondered? These harmless jellyfish breed in the nearby Ala Wai Boat Harbor and might drift to the waters of Ala Moana Beach Park.

Still, I've not heard that these calm-water, nonstinging creatures get over there. Box jellyfish and Portuguese men-of-war, yes, but if you run into one of those, the encounter is not a touch; it's a sting.

An experienced swimmer at the reading spoke up. "The most terrifying thing in the water to me is a plastic bag. One run-in and I'm jumpy for the rest of the swim."

"But you can see a plastic bag," someone else said. "We're talking about something hard to see."

Might this thing be seaweed, I said? We Hawaii swimmers know well the panic that a drifting piece of seaweed can cause, especially in murky or rough water. But everyone agreed that pieces of floating seaweed big enough to feel are also big enough to see.

The group moved on to other subjects, but this mysterious marine touch stayed with me. Finally, I settled on salps.

I didn't mention these gelatinous creatures at the time because they're not only hard to see, they're hard to describe.

But now that I've had time to think about it (OK, and to look it up), I can explain a salp.

Salps are mostly transparent tubes with openings at each end, like a toilet paper roll. They range in size from a half-inch long to more than 12 inches long.

These creatures get around by jet propulsion, contracting their tube walls to push water in one end of their bodies and out the other. By opening and closing either end, a salp can go in either direction.

Salps are incredibly efficient. Their water-pumping system provides sensory input, respiration, waste removal, sperm dispersal and food. While moving through the water, salps cast out a mucus net to catch and eat plankton. When alarmed, salps drop their self-secreted nets and stop feeding.

Salps are among the fastest-growing animals in the ocean. Under ideal conditions these creatures form swarms containing millions of individuals. Population growth rates in salps can be 10 to 100 times that of other zooplankton.

Millions of salps generate a lot of waste material, but it's quickly recycled. Salps' fecal pellets sink fast and nourish midwater and bottom-dwelling creatures.

These soft, see-through creatures sometimes form chains several feet long to share sperm and eggs. Such pulsing chains are beautiful to behold.

They're also, I imagine, creepy to swim into.