Under a crescent moon and starry sky, a crowd dance to the ambient electro beats of Floating Points in a stone amphitheatre – it’s an idyllic setting for a gig. I’m on Obonjan, a previously uninhabited Croatian island that aims to be both a summer-long festival and a wellness retreat – and the atmosphere is upbeat yet relaxed.

Things hadn’t started quite so well. Obonjan was slated on social media when it failed to open for its six-week season on 28 July, citing water and electricity supply issues. People had to abandon holiday plans at short notice. Refunds and rebookings were made, but the burning question when I join the island’s first guests is whether this ambitious project is now ready to party.

“It was devastating to let people down and not open after working on this for four years, but we’d no choice,” says co-founder Dan Blackledge, the man behind Croatia’s Unknown and Hideout festivals, who blames contractors for last-minute failures. It is a shame, because a lot of passion, creativity and hard graft has obviously gone into this truly exciting idea.

Facebook Twitter Pinterest A DJ playing at one of the bars.

It’s a 40-minute boat trip (20 by speedboat) from Šibenik, 80km from Split, to Obonjan, past uninhabited isles and an abandoned island fort. A DJ is playing on the deck of Drift bar as we arrive and people are swimming in the translucent Adriatic and lounging on oversized beanbags sipping cocktails. So far, so cool.

Accommodation for up to 445 guests is in bell tents or safari-tent style “lodges” sleeping from one to four, scattered among the pretty pine forests (you can’t bring your own tent). All have wooden decks, air-conditioning, electricity, proper beds, towels and sheets. I’m impressed with our lodge, which has a fridge and en suite too. It’s all very tasteful with thoughtful touches – deckchairs on the terrace, gorgeous rugs and bed covers, hampers with cutlery and crockery, even hanging baskets with plants.

Finishing touches are still being added (the Zen Den’s healthfood cafe has opened since I left) and there’s landscaping to be done, but it already feels magical. There are hidden coves to discover, paths winding through the woods, chirping cicadas a constant soundtrack. Eden Labs (the international creative partner of the Eden Project) advised on all sustainable development, helping to keep the environmental impact to a minimum – and the sense of untamed nature is tangible. We explore the 136-acre island, struck by how wild it all still feels, and then head to The Kitchen, the main restaurant and bar by the vast saltwater pool for dinner. The vibe is relaxed Ibiza, the view amazing.

Facebook Twitter Pinterest Bell tent accommodation.

It’s here, though, that teething problems start to show, with long waits and chaotic service, despite the lovely staff. The food, however, is delicious and faultless: spicy tempura shrimp (£5), dorado with red pepper (£14).

Wellbeing is central to Obonjan’s philosophy and I’m up early for a yoga class on a shaded platform. There are several classes a day, led by inspiring teachers, and an ever-changing programme of holistic workshops – from “manifesting magic” to group hypnosis (all activities are included in the price, except spa treatments and excursions). Besides satisfying dedicated yogis, the aim is to appeal to newbies who might want to dip in between gigs too. “My sister’s the festival lover, but I’m here for the yoga,” said Sabrina, a headteacher from Shrewsbury. “The combination works really well for us.”

For party action, the Forest Bar is a fun spot, with DJs playing under illuminated trees in front of a giant mural. It seems less messy than many festivals (maybe due, in part, to the small scale) with a grown-up vibe, the international crowd mostly mid-twenties up (under-18s aren’t allowed). “I think we’ll attract people who’ve done their hardcore partying,” says Dan. “You can have fun but chill too, and you don’t need to cram it into three days.”

Facebook Twitter Pinterest A yoga session.

Comedian Sara Pascoe and spoken-word artist Kate Tempest are on the bill later in the week, Gilles Peterson is among dozens of visiting DJs, and talks, film screenings, kayaking, stand-up paddle boarding and sailing trips start soon. Visiting artists will be leaving their mark on the island, too, with paintings, sculptures and installations popping up over the summer. Plans for the future are yet more ambitious: treehouses (capacity will grow to 800), family weeks, an eco research centre with Eden Labs, marine conservation projects, banquets – and opening will be extended, from June to October. “There are so many big ideas and great people involved. We want Obonjan to be a platform for connection and community,” says Dan.

But the major problem during my trip is the food – not quality but quantity. Bok, the lovely waterfront restaurant serving delicious small plates, can’t cope with demand one lunchtime and closes the kitchen, and there’s confusion over what’s open when. The Pavilion pizza takeaway is a back-up, and the Corner Shop has basic supplies, but some guests take trips to the mainland to stock up, and others complain of high prices.

True, an unexpected storm contributed to the chaos, and more staff start this week, but things need to improve rapidly. If you’re thinking of visiting, perhaps it’s safest to wait until late in the season or even next year.

Facebook Twitter Pinterest A tarot card reader ‘manifesting magic’.

“Things did go wrong, particularly on the food side, but you forgave it because it was the first week and overall it’s amazing,” said Grant from Melbourne. “It’s sure to be a big hit – we loved the mix of yoga and partying. I’m hoping to come back for my 40th.”

• The trip was provided by Obonjan (obonjan-island.com), which runs until 7 September. Bell tents from €72pppn and lodges from €97pp; transfers €14 each way. For further information visit croatia.hr