Greg Mortimer, photo by Sergei Andronov.

SunStone's Chinese-built expedition cruise vessels

Designed by Ulstein and built at CMHI in China, the INFINITY Class expedition cruise vessels are purpose-built for small-scale, high-comfort exploration. With seven vessels delivered, most recently Douglas Mawson in September 2025, the series demonstrates how proven design, serial shipbuilding and operational feedback deliver long-term value for expedition cruise operators.

From Greg Mortimer to Douglas Mawson

The INFINITY Class represents a new generation of expedition cruise vessels developed for SunStone Ships. Based on Ulstein’s CX103 design and featuring the distinctive ULSTEIN X-BOW®, the series combines safety, comfort and efficiency in some of the world’s most demanding operating environments.

Since Greg Mortimer's delivery in 2019, the fleet has steadily expanded. Seven vessels have now been delivered: Greg Mortimer, Ocean Explorer, Ocean Victory, Sylvia Earle, Ocean Odyssey, Ocean Albatros and, most recently, Douglas Mawson.

A proven design platform refined through series building

All INFINITY Class vessels share the same fundamental design philosophy and hull form, allowing experience from daily operation to be incorporated from one vessel to the next. This serial approach reduces technical risk, improves build efficiency and enables continuous optimisation of performance, comfort and operability.

The vessels are 104 metres long, with a beam of 18 metres and a draught of 5.1 metres. Passenger capacity typically ranges from around 130 to 200, depending on operating area and regulatory requirements, supported by a crew of approximately 85–115.

Ulstein Design & Solutions AS is responsible for the exterior design, while Tomas Tillberg Design has developed the interior concepts.

Comfort at sea – confirmed by operators

For expedition cruise operators, vessel motion, noise levels and onboard comfort are critical to the overall guest experience. Aurora Expeditions, which operates three Ulstein-designed INFINITY Class vessels (Greg Mortimer, Sylvia Earle and Douglas Mawson), has shared consistent feedback based on several years of operation.

Both the Greg Mortimer and Sylvia Earle have exceeded expectations. Expeditioners consistently tell us that the smoother ride, reduced slamming, and lower noise levels make a huge difference, especially on longer ocean crossings.

Katie Malone, Chief Marketing Officer at Aurora Expeditions

Many guests travelling with Aurora have prior experience from other expedition vessels and immediately notice the difference. Reduced vibration and improved seakeeping contribute to better rest, increased comfort and greater use of public and observation areas on board.

Douglas Mawson – the latest addition to the fleet

Delivered in September 2025, Douglas Mawson is the seventh INFINITY Class vessel. Like her sister vessels, she is designed for both polar operations and warm-water expeditions, with flexible layouts and capacity depending on itinerary and area of operation.

The vessel supports Aurora Expeditions’ operational profile, combining efficient logistics for expedition activities with open, light-filled public spaces. The design emphasises proximity to nature and functionality for education, observation and exploration throughout the voyage.

Douglas Mawson Sydney 1

Operational flexibility across regions

Although originally developed with polar expeditions in mind, the INFINITY Class has proven equally well suited for operations in warmer regions. The vessels’ compact size, manoeuvrability and robust design enable access to remote destinations that are inaccessible to larger cruise ships.

This flexibility allows operators to extend seasons, diversify itineraries and deploy the same vessel across different regions throughout the year, while maintaining a consistent onboard experience.

Sustainability by design

Sustainability is an integral part of the INFINITY Class concept. The vessels feature diesel-electric propulsion, energy-efficient systems and waste-heat recovery. Combined with the ULSTEIN X-BOW®, which reduces resistance and improves fuel efficiency, these solutions contribute to lower energy consumption and reduced emissions.

For expedition operators, sustainability is also closely linked to scale and intent – operating smaller ships, limiting passenger numbers and placing education, science and environmental awareness at the core of the travel experience.

Long-term value through collaboration

The INFINITY Class illustrates the value of close collaboration between owner, designer, shipyard and operator. Through continuous feedback and refinement, the series has evolved into a robust, future-oriented platform for expedition cruising.

From Greg Mortimer to Douglas Mawson, the INFINITY Class demonstrates how thoughtful design and operational insight can create lasting value for owners, operators and guests alike.

The INFINITY Class vessels

INFINITY Class – key facts

Length
104 m
Beam
18 m
Draught
5.1 m
PAX capacity
130-200
Crew
85-115
Vessels delivered
7