LEARN ABOUT THE CROWN-OF-THORNS STAR

April 7, 2025

The crown of thorn Starfish are found on nearly every site we visit on the Kohala Coast. Divers often ask us after a dive “What was that cactus looking thing” or “was that a weed on the coral?” Read on for some info on these interesting invertebrates.

A close up of a sea star on a coral reef.

While enjoying the reefs of Hawaii and all their marine life, spare a thought for the corals on today’s menu!


The diner is Acanthaster planci , Crown-of-Thorns star (COTS) and his favorite meal is coral polyps, especially those of Pocillopora meandrina (Cauliflower coral).


The body is disc-shaped, up to 18” across, with as many as 21 arms, it’s usually red/green in color and the whole thing is covered in venomous spines. Don’t get too close…many divers will tell you of their discomfort having inadvertently got too friendly with this star (burning pain, numbness and possible discoloration of the area for a couple of days)!

While enjoying the reefs of Hawaii and all their marine life, spare a thought for the corals on today’s menu!


The diner is Acanthaster planci , Crown-of-Thorns star (COTS) and his favorite meal is coral polyps, especially those of Pocillopora meandrina (Cauliflower coral).


The body is disc-shaped, up to 18” across, with as many as 21 arms, it’s usually red/green in color and the whole thing is covered in venomous spines. Don’t get too close…many divers will tell you of their discomfort having inadvertently got too friendly with this star (burning pain, numbness and possible discoloration of the area for a couple of days)!


They are impressive creatures, using all of those arms to climb atop coral colonies where they then extrude their stomachs and secrete enzymes to liquify & digest individual coral polyps. Just the white coral skeletons remain, when they absorb the available nutrients and move on. True horror movie stuff!


While these stars have wreaked havoc on some reefs around the world (including the Great Barrier reef), here in Hawaii we don’t appear to have a big issue with them yet, and usually, one won’t see more than a few at any one site. In places where they have become a real issue, divers can physically remove the creatures or inject them with household vinegar to kill them… although either option is time-consuming & costly.


There are some in Hawaii who believe that this predator may in fact be doing some good for the reef, feeding on some good for the reef, feeding on some of the faster-growing corals (such as Cauliflower & Rice corals) and increasing coral diversity on Hawaiian reefs.


In Hawaii, their main natural predator is the Triton’s Trumpet snail; also Harlequin Shrimp, Stripebelly Pufferfish and Lined Fireworms will feast on this star.


We hope you will get a chance to observe this impressive star, when diving with us at Kohala Divers in Hawaii!

A scubapro scuba diver is swimming in the ocean
By Rebekah Kaufmann June 25, 2025
I began my journey into Scuba as a very nervous participant. I did not consider myself a very adventurous person and was coerced by a significant other to try Scuba. I was living in the pacific Northwest. Surrounded by cold and mysterious salt water bays, sounds and canals. I was fascinated by everything about the underwater world except going into an environment inhospitable to human life. When I finally was convinced to sign up for an open water scuba class I was terrified. I read the PADI manual cover to cover twice before the first class (this was before eLearning existed) I was sure there was so much technical skill and memorization I’d need to master to make it out alive from my first dive. The night before my first session I called the instructor to tell him this just wasn’t for me. I was terrified and I was pretty sure I did not have the ability to survive the pool session the next day. He asked me to please give it a try. He didn’t want to break his record of no student quitting on him and would I just get in the pool and see what happens. No pressure to continue after that. I reluctantly agreed. I over thought every skill in the pool and awkwardly made it through the skills development sessions. My instructor kept reminding me “relax this is fun”. So far to me the stress of getting it right was over shadowing any fun to be had. The weekend finally came to do the open water check out dives. We were going to a popular “easy” shore diving spot called Illahee state park. It was a pebble beach with a long wooden dock with tall tar covered pilings with muscles and seaweed growing off of the stretches exposed from the low tide. It was early fall so air temperature was mild but still we poured ourselves into double layer 7mm farmer John style wetsuits to keep warm In the frigid 44 degree water of the puget sound. 7 mm hoods gloves and boots and I no longer felt, looked or moved like a human. Our class of 5 waddled towards the sea fins in hand following our instructor and his assistant. As we donned Fin’s and defogged our masks I was mildly panicking trying to reenact everything I’d learned and imagining (dreading) going below the black surface of this frigid water. The plan was to start descending near a piling for reference. We did our buddy checks. BWRAF which of course I’d memorized from my panic studying. The other students raised their deflators. And carelessly dropped below with the dive pros. I added more air to my BC and started to cry. The assistant instructor stayed below with the other comfortable divers and my instructor re emerged from below. Did you forget which button to push to release air he asked? “No” I said “but I think I’m pretty cozy right here. Did you see how pretty the sky is today? Up here. Where we can breathe air? Without monitoring it? “ He laughed and asked if we could just put our regulators in and hold the pier and just let our heads go under. See what it’s like down there. No pressure. We can come right back up. Well ok I could handle that. As I released the air from the BC I found I didn’t drop out of control like I’d feared. In fact I could control it by exhaling. I was still pretty wide eyed and in my head but it was ok. Then Jim my instructor pointed at the piling. There on a slimy black mound of algae was the most fluttery, colorful nudibranch you could imagine. Just slowly sliming his way along the pier. He had spiral spikes coming from his head and soft feathers coming from his back. I’d never seen anything like it. I moved closer and saw scattered below that was starfish in multiple colors laying over each other in a kaleidoscope of colors. Below that anemones opened and closed as they swayed in a gentle back and forth motion. Keeping to his word Jim gave me the thumbs up to signal we could kick back to the surface from the 8 feet we’d descended. Before I could even get the regulator out of my mouth I was babbling about how cool the slug was and did he see the starfish and what was that soft sock looking thing with tentacles. I was giddy. He just smiled. Want to join the others for open water dive one. YES. Once I got out of my head I enjoyed every minute under water. The sinking descent controlled by an exhale. The tiniest touch to your Bouyancy device allowing you to position and stay weightless. The ease of sipping just the air you need without thought. The sound of bubbles that take over the chatter from above. I’d found my happy place and I’ve never looked back. Fast forward 25 years later and I own a PADI 5 star dive business on the big Island of Hawaii. I’ve worked as a dive instructor for my entire career and now get to provide an environment for other budding instructors to live their passion and bring more new divers into the world of SCUBA. To this day my favorite part of teaching diving is to those that it doesn’t come easily to. Bring me your terrified, your nervous, your overthinking land lovers that are curious about what it’s like beneath the sea and willing to try something they are scared of. When my good friend Christine expressed interest in giving diving a try I was drop jawed. Since I’d known her she could barely get on a boat. Swimming in a 4 foot swimming pool conjured up fears of the megaladon for her. Perfect I thought. I’m always up for a challenge.  Her drive to learn scuba was to be part of her family’s adventures since they were divers. Also she wanted to prove to herself she could face her fears. For many fear of deep water runs deep. Since it’s my passion to help new divers overcome fears and find peace underwater I wanted to learn more about where these fears come from. Here are the main reasons people fear deep water:
By Rebekah Kaufmann April 29, 2025
Exploring the underwater world for the first time can be life changing!!
A pair of serene scuba diving goggles laying on a hawaiian towel
April 7, 2025
Is this you?!?! Do you exhale in your socially-distant mask and fog your glasses? Well, the people who de-fog your scuba mask have some advice: