Morska oaza Piran · Sea Oasis Piran

45°29'17.5" N  ·  13°35'01.0" E

One kilometre off the Slovenian coast, on a flat muddy seabed with almost no natural hard substrate anywhere, sits a handmade reef. The Sea Oasis Piran is the first and only underwater structure in Slovenian waters — built from eco-concrete and limestone, designed to last a century, and lowered to the seabed on Earth Day, 22 April 2024. Life arrived within four months.

Days in the water

—

since 22 Apr 2024

Days since first life

—

polychaetes & bryozoa, Aug 2024

Species groups confirmed

6+

and counting

Depth at site

10–12 m

seabed · structure summit at ~7m

Dimensions

5.5 × 3.5 m

length × width · 3m high · 5 growth plates

Built to last

100+ yr

eco-concrete · limestone · calcium carbonate

Distance from shore

1 km

Gulf of Piran · Slovenian territorial waters

Descent to the Oasis

depth explorer

drag the slider to descend from surface to seabed

0m
0m
12m
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Surface
You are at the surface of the Gulf of Piran, 1 km from the Slovenian coast. Below you: 10–12 metres of water to the seabed. The Sea Oasis sits on the bottom — drag the slider down to descend.
↓ drag to descend · structure at 7m

Life takes hold

Apr 2024
installation
Aug 2024
first life · 4 months
Jan 2026
22 months
Mar 2026
art colonised
ongoing
monitoring continues
Earth Day, 22 April 2024. The Sea Oasis Piran is lowered to the seabed of the Gulf of Piran — the first underwater structure in Slovenian waters. A vision first conceived by marine biologist Ugo Fonda in 1990, finally realised 34 years later with full funding from BAUHAUS. The structure settles on the muddy bottom. The seabed around it is bare.

Residents & visitors

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V spomin velikim · In Memory of the Greats

Artistic sculptures · Pinna nobilis · Sea Oasis Piran

✦ first organisms confirmed — march 2026

The noble pen shell — Pinna nobilis, or leščur — is the largest bivalve in the Mediterranean. It once grew abundantly in the Adriatic, reaching up to a metre in length. From 2016, a parasitic outbreak swept through Mediterranean populations and devastated them. Very few wild individuals remain.

Artistic interpretations of the pen shell have been placed within the Sea Oasis as tribute and as habitat. In March 2026, the first organisms were confirmed settling on these sculptures — a milestone for what YouSea calls an underwater gallery. Art and science, in the same act of giving something back to the sea.

the vision was first conceived in 1990. it took 34 years, a committed team, and a sponsor who believed — but the sea is already responding.

The vision behind the Oasis

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Marine biologist · diver · visionary · † 2011

Ugo Fonda

In 1984, Ugo Fonda founded an underwater activities company in Piran — construction, harbour maintenance, marine sampling, underwater filming. A biologist and professional diver, he became one of Slovenia's most respected experts on the Adriatic, with work spanning the Mediterranean and Atlantic. The sea was not his profession. It was his conviction.

In 1990, he first conceived the idea of an artificial reef in the Gulf of Piran — a sanctuary for the fish, crabs, molluscs, and invertebrates disappearing from the silted, degraded seabed. He planned it carefully. He spoke of it often. He spent years trying to make it happen.

He died in 2011. His daughter Irena and son Lean — both biologists — carried the family business forward and eventually founded YouSea to bring his idea to life. The Sea Oasis Piran was lowered to the seabed on Earth Day, 22 April 2024. Thirteen years after his death. Thirty-four years after the first sketch.

His presence is felt daily in the way my brother and I approach the business. — Irena Fonda

Sea Oasis quiz

5 questions · test your depth

Visit the Sea Oasis Piran

Book a 2.5-hour underwater drone tour and watch the structure and its inhabitants from the surface. Or join a guided coastal walk with marine biologists, or a snorkelling trip over the seagrass meadows. The sea is at its best when you know what you're looking at.

Book a tour · info@yoursea.org Explore YouSea → View location on map →
Main sponsor & partner BAUHAUS