Unbelievably, I was located somewhere between two islands. Out in the open sea, the inky blackness of genuinely deep water beneath me, I was trying hard to keep my mind from replaying scenes from Jaws and Open Water as I battled with my own primal fears. In fairness, this was the first real moment of near panic I'd experienced so far in my sea swimming trip to the Sibenik archipelago and Kornati Islands National Park in Croatia. Until now, it had all been going, well, swimmingly.
Billed as a "short swims" trip, suitable for those with little or no open-water experience, it had sounded like just the ticket. I knew I could manage the predicted distances; it was just the mind games involved in swimming a straight line in deep water rather than laps in a pool I had to contend with. After an initial assessment swim off the jetty near the hotel base on the tiny island of Krapanj, I'd been allocated a place in the slowest team, which came as no surprise to me. Sticking to breaststroke I knew I wouldn't be winning any prizes for speed, but I could at least just keep going, pretty much indefinitely, or so I hoped, across the Adriatic.
The clear blue waters of Croatia could soon be welcoming even more tourists. Eight days from now, the nation takes a plunge of its own: it joins the EU on 1 July, to swim in the choppy waters of economic integration.
During my stay, the water was reassuringly calm. The format for each day was the same: the boat would drop each team off the back at intervals designed to accommodate differences in pace and everyone would start swimming. It was that simple. The chill of the sea was soon forgotten, replaced by the soothing effect of my motion through the buoyant water, the sun shining down and splintering into glittering shards below.
Along the coastline of Zlarin, there was so much to see beneath the surface. I was delighted to be taking things slowly enough to spot starfish and sea cucumbers; even the odd sponge was visible on the seabed. Despite, or perhaps because of, the fact that sponges were once such big business in this area – the hotel I was staying in was named the Spongiola – very few now populate the clear waters of the Adriatic.
As fascinating as the sea cucumbers were, it was the fish that really had me charmed. Gliding alongside unpopulated rocky islands, I was frequently startled by a sudden surge of silver flashing by in a swirling simulacrum of the sun's rays. I'd certainly become a much more economical swimmer since arriving, expending far less effort than when I arrived to travel the 3km a day or so that I had been swimming, but I'd still never achieve the innate piscine grace of that school of fish beneath me, disappearing off into the dark depths.
A visit to the Krka National Park, known for its waterfalls, made a relaxing change after a couple of days at sea. However, this was no dry day, with a splash around in the fresh water of the spectacular falls followed by a self-powered journey back along the brackish river from Skradin to near Sibenik itself, pleasure cruisers filled with tourists passing at a distance. I imagined they were probably puzzled to see small packs of swimmers making their sedate way.
After a morning swim of about 1.5km to 2km, lunch back on the boat was always devoured. On Zlarin, while I'd joined in swapping treading water for a hillside walk to the highest point on the island, the captain of the boat had sourced a rare treat. Jumping off the boat, he'd harvested mussels from the harbour walls and cooked them in seawater. After all that exercise I'd never tasted anything so delicious.
Sitting in the sunshine, chatting with my fellow swimmers, it was pretty clear we all had our individual anxiety responses to the open water. For me it was about depths, while others weren't keen on submerged objects or seaweed. Thankfully, there didn't seem to be anyone along who was nervous around fish, a problem I had encountered among lake swimmers back home.
The crossing between the islands of Krbela, Oblik and Drvenik was a high point of the week, not least because of the sense of achievement gained from talking myself down from my fears.
Combining the safe feeling of shoreline swimming, with sections of open water and aquatic agoraphobia, this was an experience I'd never even come close to encountering before, and certainly not in my local pool. Glimpses of the shocking pink hats of my fellow swimmers and the safety dinghy were all the visual markers I had, other than the shore of the next island which seemed a million miles away.
In front of a stunning platter of local seafood with a single beer, it was hard for me to imagine that I'd swum about 17km during the course of my week in Croatia. I was genuinely impressed with myself for progressing beyond the boundaries of a 25m chlorinated pool to swimming down rivers and between islands. There was a pleasing sense of symmetry, too.
One thing was certain, though. It would be a while before I would be able to face trading my darting fishy friends for the discarded sticking plasters of my local pool again.
Lara Dunn travelled with SwimTrek (01273 739713; swimtrek.com) on the seven-day Short Swims Croatia trip, which costs from £790pp, including half-board accommodation, but not flights. Trips run in June, July and August.
Flights to Split from the UK are available on Croatia Airlines (020-8745 4683; croatiaairlines.com), easyJet (0843 104 5000; easyJet.com), Norwegian (020-8099 7254; norwegian.no) and Jet2 (0871 226 1737; jet2.com). Ryanair (0871 246 0000; ryanair.com) also flies to Zadar, about 85km from Krapanj.