Kostrena – May 2024

Scuba diving in May was mostly done in Kostrena, Croatia. The conditions were slightly worse than usual, likely due to the weather, which was quite standard for this time of year.

The water temperature is slowly rising and it came to a comfortable 16°C in shallow water. I consider 16°C to be a breakpoint where you can scuba dive comfortably in a wetsuit without much additional protection.

I tried to focus and find as many nudibranchs as possible. Including all previous dives, I found quite a few different ones in Kostrena now.


This time I will start with the best one. Two examples of a small Berghia coerulescens. This was the second and third time I saw one, and the first time was also in Kostrena. Unfortunately, both were quite difficult to access with my camera.

Berghia coerulescens Berghia coerulescens

Next are Flabellina ischitana on the left and Flabellina pedata on the right. Both were on the smaller end. You can see there was a bit of current on the right picture which the Flabellina was handling quite well.

Flabellina ischitana Flabellina pedata

Lastly a dotted sea slug (Peltodoris atromaculata) on the left and Thuridilla hopei on the right. Both are very common here.

Peltodoris atromaculata Thuridilla hopei

In general, there weren’t that many nudibranchs, but compared to previous weeks there were more of them. Most are still quite small though. However, including the ones I saw in April, there were quite a few different species.

Other organisms

Starting with fish, the red scorpionfish (Scorpaena scrofa) is a common sight there and you can on occasion see some that are quite large. Next is also a common fish, likely a Parablennius incognitus.

Scorpaena scrofa Parablennius incognitus

You can find crystal prawns (Periclimenes scriptus) hiding in golden anemones (Condylactis aurantiaca) almost always. This is a very good example of how much more you can see if you swim slowly and carefully look everywhere. It also helps to know what you are looking for. This time we only found one spiny lobster (Palinurus elephas) of a smaller size.

Periclimenes scriptus Palinurus elephas

The sunset cup coral (Leptopsammia pruvoti) is a solitary coral and they look extremely nice if you get a good photograph. The Mediterranean feather star (Antedon mediterranea) in yellow color didn’t have a crinoid shrimp this time, unfortunately.

Leptopsammia pruvoti Antedon mediterranea

And another very nice find, a greater pipefish (Syngnathus acus). You can usually find them on the sandy bottom so they are often missed, as most of the dives are done along a wall. This is a relative of the seahorse and you can certainly see the resemblance if you look at its head.

Syngnathus acus


This was just a small part of what we saw. There were a nice couple of dives over a few weekends. Next time I will try to take a video of schools of small fish that you could just sit and watch.