Kostrena – 19.4.2024 – 22.4.2024

An extended weekend meant it was time to go scuba diving in Kostrena, Croatia. While the forecast was not that good initially, the weather did hold up well enough. In total, I did seven dives as the winds picked up on the last day so I only did one dive then.

The water temperature was 14°C – 15°C, with maybe 16°C at the surface. The visibility was fair, certainly nothing to complain about.

There was plenty to see. The highlight of the whole trip was a rather large tuna that I managed to glimpse for only a second. I was extremely lucky that I was looking out into the blue at the right time. I am not entirely sure of the exact species, likely it was the bluefin tuna (Thunnus thynnus) and it was about 100 cm long and moving relatively fast. There was another highlight of which I have pictures. It was a huge lobster (Homarus gammarus) and it was double the size of the largest one I saw to date.


One of the most colorful animals are easily the nudibranchs. They come in a variety of colors and shapes. First, a few common ones that I regularly see during my dives.

The dotted sea slug (Peltodoris atromaculata) is a common sight but I rarely get a chance to see one with its rhinophores and gills visible. This time there were several such occasions. Thuridilla hopei was a common sight as well. I had difficulties getting a good picture though, as they are small and most of the time they weren’t out in the open.

Both flabellinas, Flabellina pedata or Edmundsella pedata, and Flabellina ischitana or Paraflabellina ischitana were a nice sight, but this time I only saw a few. I think they will be more common in the following months.

And lastly, the Elysia timida was plentiful in the shallows. It’s nice when I have something to do during my safety stops.

Peltodoris atromaculata Thuridilla hopei Edmundsella pedata Paraflabellina ischitana Elysia timida

Next are a few that I don’t see that often, or at all. First is the Limacia clavigera which I believe I saw for the first time. Next to it is the Felimida luteorosea which I also saw for the first time and I am quite happy with the picture.

Lastly, the Phyllidia flava which I do see on occasion, but normally it is just an orange blob with its rhinophores retracted. This time, I got very lucky to see it this way.

Limacia clavigera Felimida luteorosea Phyllidia flava


Normally I don’t take pictures of fish as they don’t tend to stay still. However, every once in a while I come upon one that doesn’t mind me and I can take a few nice photos.

The first is likely a male triplefin blenny (Tripterygion tripteronotus or Tripterygion delaisi). It was positioned perfectly for this photo. Next, an axillary wrasse (Symphodus mediterraneus) with a photobomb from a female Mediterranean rainbow wrasse (Coris julis) on the left.

The small red scorpionfish (Scorpaena notata) and the red scorpionfish (Scorpaena scrofa) are venomous and a common sight. They can move rather fast when annoyed so I keep a bit of distance and try not to bother them too much.

Lastly, likely a variety of a golden goby (Gobius auratus) which is similar to the Yellow-headed goby (Gobius xanthocephalus) that is found in a different region.

Tripterygion tripteronotus Symphodus mediterraneus Scorpaena notata Scorpaena scrofa Gobius auratus


Yellow cluster anemone (Parazoanthus axinellae) is always nice to see. I often try to take a few pictures of them if I see a good composition. Besides it is the sunset cup coral (Leptopsammia pruvoti) which is a solitary coral.

Parazoanthus axinellae Leptopsammia pruvoti


I was really glad to see this one. It is likely a greater pipefish (Syngnathus acus) and is a close relative of the seahorse. Looking at the head and snout you can certainly see the resemblance to a seahorse.

Syngnathus acus


First, a few pictures of symbiosis. Various organisms in the ocean live with each other in a way where they both benefit from one another. For example, one organism may get protection and the other cleaning.

On the left is a golden anemone (Condylactis aurantiaca) with what is likely a crystal prawn (Periclimenes scriptus). On the right is a Mediterranean feather star (Antedon mediterranea) with a well-hidden crinoid shrimp (likely Hippolyte prideauxiana) behind it.

With the crinoid shrimp, I saw that I still need to work on my observation of shrimps as I usually miss most of them. Often I only see them later in the pictures as was the case here.

Periclimenes scriptus Hippolyte prideauxiana

And here is the second highlight, the common lobster (Homarus gammarus). You can see from the picture, that it was huge and quite old. Its claws were easily the size of my forearm, which I didn’t directly test for obvious reasons.

Next to it is a much smaller example of a spiny lobster (Palinurus elephas). And lastly a nice looking squat lobster (Galathea strigosa). They don’t normally stay still for such a long time, but this one didn’t mind me. It went a bit into the hole but didn’t hide like they normally do.

Homarus gammarus Palinurus elephas Galathea strigosa


Overall I had a great four days of scuba diving with a lot of different things to see on each dive. The weather also held up quite well.

Even though the house reef area is small in comparison to some other locations, you can always see a lot on each dive. The pictures above are just a small portion of what I saw.