I now have hundreds of itchy bites over my legs and arms, and some on my torso. I realised that this must be due to the so called sea lice that were trapped in my long wetsuit when I went windsurfing from the centre of the beach at Sandy Cape, north of Jurien Bay. They are actually tiny jellyfish larvae that got squeezed by the wetsuit, which is tightest on the limbs. No bites outside the wetsuit. Very uncomfortable and difficult to sleep, but slowly getting better now.

Didn't see any jellies around. Don't know if I picked them up near the beach or further out when I let water into the suit to cool down.

Does anyone know if they are seasonal or unpredictable like jellies?

Pretty sure it wasn't ticks. My partner was doing everything that I did, except put on a wetsuit, and she suffered no effects. I think the larvae get crushed where the wetsuit is very tight and this is exactly where the bites are. They are only slowly getting better after a week.

Mine look just like this: www.healthline.com/health/sea-lice-bites#symptoms