SHERIDAN, WYOMING -- August 14, 2026 -- The SEA Index®, developed by the Yacht Club de Monaco in partnership with Lloyd's Register, has broadened its environmental assessment methodology to include recreational boats starting at 10 meters, a category that now covers series-built vessels and catamarans previously outside its scope. The expanded framework relies on new reference models built from an extensive dataset and aligned with international maritime energy efficiency principles. For boatbuilders, brokers, and fleet operators, the change means a wider swath of the pleasure-boating market can now be measured against consistent, verifiable emissions benchmarks rather than relying on isolated or incomparable data points.
New Benchmarks Target Series-Built Boats and Catamarans
Until now, the SEA Index® primarily served the super-yacht segment, where design and performance data tend to be more standardized and closely tracked. The updated methodology extends that same rigor downward to smaller, mass-produced boats and catamarans, vessel types that vary widely in hull form, propulsion, and typical usage patterns.
By tailoring reference curves to these design and operational differences, the index aims to let owners, buyers, and charter operators compare a given boat's carbon performance against a benchmark suited to its actual class, rather than an average that may not reflect how the vessel is built or used.
Methodology Anchored in IMO Decarbonization Measures
The recalibrated models were built using a large body of vessel data and follow methodologies consistent with International Maritime Organization decarbonization measures. That alignment matters for shipyards and fleet managers who increasingly need to demonstrate environmental performance using criteria that regulators and financiers already recognize.
Rather than a single blanket standard, the index now differentiates between hull types and speed regimes, reflecting the reality that a planing series boat and a displacement catamaran do not share the same efficiency profile even at similar lengths.
Executives Frame the Move as an Industry-Wide Step
Bernard d'Alessandri, President of the SEA Index® and Secretary General of the Yacht Club de Monaco, described the expansion as a significant milestone not only for the index itself but for the wider boating industry. He noted that applying the methodology to recreational boats from 10 meters upward, including series units and catamarans, makes environmental assessment more inclusive and accessible, with the broader goal of helping establish a shared, credible, and transparent framework capable of supporting environmental performance gains across the global recreational fleet.
Dr Chris Craddock, Global Lead for Marine Asset and Operational Performance at Lloyd's Register, said the methodology has been refined to better capture the range of operational profiles found among series-built yachts and super-yachts, along with the meaningful hydrodynamic differences tied to hull form and speed. By benchmarking vessels against specific reference curves developed through rigorous methods consistent with IMO decarbonization measures, he said the index provides a fair, transparent, and internationally consistent framework for assessing environmental performance across the yachting sector.
Wider Access to Independent Emissions Data
Extending the index's reach beyond super-yachts gives a larger pool of builders, brokers, and owners access to an independent framework for evaluating CO2 output. That matters for buyers weighing resale value or charter viability, and for yards needing to substantiate sustainability claims with third-party data rather than internal figures alone.
The organization behind the index frames this as part of a more structured, inclusive transition for recreational boating overall, one where smaller and series-built vessels are no longer excluded from the kind of scrutiny previously reserved for larger custom yachts.
Growing Verified Dataset for the Wider Market
Incorporating smaller boats and production models into the index is also intended to build a deeper, more comparable dataset on sector-wide CO2 emissions. Over time, that could give charter companies, financiers, and regulators a clearer picture of where the recreational fleet stands collectively, rather than relying on fragmented figures from individual builders or class societies.
Lloyd's Register's advisory arm, which supports maritime and energy clients on decarbonization, digitalization, and regulatory change through a team of more than 250 specialists, contributed its technical expertise to the recalibrated models, lending the index additional credibility with operators already familiar with Lloyd's Register's broader classification and advisory work.
Boatbuilders, brokers, and fleet operators interested in how the expanded SEA Index® methodology applies to their vessels can find more information at https://www.yacht-club-monaco.mc.