Jellyfish
Swimming with Jellyfish by Mark S
This is adapted from a post from the TnT Members' Forum, July 2023
In 2022, we had a lot of jellyfish in Hayama. Unusually, there were Portuguese man o’ war jellyfish (katsu no eboshi) which of course are very nasty. In May 2023, there were already reports of katsu no eboshi washed up on the beaches. Summer always marks the arrival of light pink/blue box jellyfish with 4 tentacles (andon-kurage). These can give a nasty sting, but it usually doesn’t last too long. There are always lots of white blobby jellyfish, but these do not seem to sting.
It is easy to get put off swimming by the jellyfish, but it is possible to swim through the whole season without getting stung if you take precautions. Here is what I have learnt from swimming in Hayama for many years.
1. Area
Due to the sea currents, wind directions, and river outlets, jellyfish tend to be concentrated in some areas and less common in others. They get pushed up to rocks, so all of the rocky promontories get concentrations, especially Najima (the island with the red torii gate), Shibasaki (the big area of low rocks and rockpools between Morito and Isshiki), and Chojagasaki (the tidal island and rocks to the left of Ohama Bay).
Of the three main swimming areas, Ohama / Chojagasaki, Isshiki, and Morito, Morito always seems to have fewer jellyfish. Once the jellyfish arrive, I mostly swim in Morito.
The other place jellyfish collect is in the shallows along the beach. I try to enter quickly, wade out as far as possible, and then swim straight out. When I return to the beach, I do breaststroke when I get near, and then stand up as soon as it is shallow enough. The main thing is to protect the face.
It is also worth asking the lifeguards about the situation on any beach. They are likely to know if it is a good day or a bad day.
2. Clothing
Neoprene is best, so wear as much neoprene as the heat allows. Rashguards help, as do close-fitting tights. The rashguard has to be as tight as possible and as long as possible. Any gap or looseness and the jellyfish can get in between the rashguard and your body. As I discovered, this is the worst of all worlds.
I bought a rashguard from Amazon US as it was hard to get the right size in Japan. I found this O'Neill rashguard to be very good.
Until it gets very hot, I wear a cheap sleeveless wetsuit over the rashguard. I have an old Orca, but Wiggle has their own-brand "dhb Hydron Sleeveless Wetsuit 2.0" for ¥9,700. Choosing a fit is usually easier with sleeveless.
Once it gets hot, I wear 2XU compression running tights instead of the sleeveless wetsuit. I also often wear neoprene swim shorts over the top - Wiggle also does these.
3. Goggles
It is easy enough to cover the body, but not the face. I wear large goggles which cover more of the face than regular swim goggles. I bought these cheap ones from Amazon and they work well. They are also useful in winter as they protect the sinuses from the cold.
4. Safe Sea sun lotion (セーフシー)
In my experience, this helps to prevent stings. Apparently, it coats the skin with a slippery surface and the jellyfish tentacles slide off. It is also a great sun lotion for swimming as it really stays on for hours. They do SPF50 and 30 and it is available from Amazon JP.
Since you can cover most of the body with clothing, you only need the Safe Sea on the face, hands and feet.
5. Treatment
I asked for advice from a local marine environmentalist who has a lot of experience with treating stings and has even experimented on volunteers who deliberately got stung. Here is his advice:
i. If the tentacles are still on the body, wash off with sea water. The tentacles have tiny needles which pierce the skin and inject poison into the body. It seems that fresh water aggravates this so only use salt water to wash off the tentacles.
ii. He recommends carrying a pair of tweezers and carefully pulling out any needles still in the body.
iii. To treat the stings, he has found Muhi Alpha EX to be more effective than vinegar. You can buy this from any drug store or Amazon JP.
