The Ocean Decade has provided a unique framework for fostering science‐informed practices that necessitate a rethinking of human relationships with the sea. The 2024 UNESCO Venice Declaration for Ocean Literacy in Action highlights the need to develop “ocean‐centric design.” While the environment‐centred design is well‐established, the ocean‐centric design remains underexplored, particularly regarding its epistemological foundations. This article defines ocean‐centric design as an approach to expanding ocean literacy dimensions and driving change across disciplines. Integrating design methodologies (civic design method) and concepts like bodies of water, Hydrocene, and perspectives from the blue humanities, the study proposes a framework and devises indicators to help designers ensure their practices are ocean‐centric. These indicators aim to foster a stronger connection with the ocean among society while addressing the Ocean Decade’s Challenge 10 “restoring society’s relationship with the ocean.” To validate these indicators, they are applied to a selection of ocean‐design case studies to assess whether the designs are inherently ocean cycle‐centric or merely contextualised within an ocean setting. Ultimately, the article seeks to expand the scope of environment‐centred design by introducing and emphasising a blue epistemology. The article introduces ocean cycle‐centric design, expanding environment‐centred design and integrating ocean literacy into resilient design practices for a restored human‐ocean nexus.

Digital twin (DT) technology has expanded far beyond its industrial origins, increasingly finding application across environmental and territorial domains. This review provides a structured mapping of DT deployments at environmental and territorial scales over the period 2020–2025, examining 117 peer-reviewed publications (109 applied studies and 8 review articles) through a structured 16-parameter classification framework. The review traces three major conceptual shifts in the DT paradigm: from industrial assets to living entities, from discrete systems to Earth-scale representations, and from closed deterministic models to ecological and systemic frameworks, as reflected in the emergence of ecological digital twins (EcoDTs), environmental digital twins (EDTs), and territorial digital twin (TDT) definitions. The results reveal a clear growth trajectory in DT applications across themes, with urban systems as the most consolidated application domain, and progressive diversification into marine, coastal, forestry, river/lake, and Earth system applications from 2022 onward. Institutional actors dominate production in this space, aligned with European flagship initiatives such as Destination Earth (DestinE) and the European Digital Twin of the Ocean (EDITO). The findings position and expand the notion of territorial digital twins as an evolving paradigm, underscoring both the momentum generated by EU digital and environmental policy and the need for integrated tools to answer and respond to key environmental challenges.

Coastal zones and their connected freshwater and marine systems are among the environments most acutely exposed to accelerating climate hazards. European policy has responded by placing Digital Twin (DT) infrastructures at the centre of its climate adaptation and ocean governance agenda: Destination Earth for the Earth system, and the European Digital Twin of the Ocean (EDITO) for the marine and coastal domain. This scoping review defines and evaluates Hydro Digital Twins (HDTs), encompassing Digital Twins of the Ocean (DTOs), coastal-zone DTs, and freshwater-system DTs, as instruments for coastal management, water territory governance, and climate adaptation decision support. Conducted in accordance with PRISMA-ScR, the review screened 231 records (January 2020 to September 2025) and retained 21 studies, each coded against a thirteen-parameter framework organised on a governance axis and a data-centric axis. Governance objectives consistently outweigh technical motivations: risk reduction dominates (7/21 studies, 33%), followed by environmental monitoring (5/21 studies, 24%) and coastal management (4/21 studies, 19%). Remote sensing is used in 19/21 studies (90%) as the near-universal data backbone; artificial intelligence, coded as an analytical method rather than a data source, appears in 10/21 studies (48%) and concentrates in the River/Lakes domain (6/7 studies, 86%), which also holds three of the four predictive outputs; citizen science data, though a stated European policy priority, appears operationally in only 2/21 studies (10%). The modal maturity category is TRL 4–5 (6/21 studies, 29%), only one study reaches TRL 6, and 6/21 studies (29%) report no formal validation. The review clarifies the architectural distinction between HDTs and Web GIS and situates these findings within the European coastal governance agendas of Destination Earth and EDITO. All proportions above are properties of the reviewed corpus and are not extrapolated to the HDT field as a whole.

Framed as a speculative essay, the text introduces the ‘Siphonophorae Society’ as a metaphor for the interdependence of human communities and water across porous land–water boundaries. Inspired by the biology of siphonophore colonies, it proposes ‘hundred-eye seeing’ as a multiperspectival epistemology that integrates human, more-than-human, and amphibious futures. It reframes ocean citizenship as water citizenship, articulating a relational mode of belonging grounded in hydrosocial interdependence. Through the Venice Lagoon, it contrasts technocratic planning with amphibious living and imagines adaptive collective futures in the Hydrocene.