Seaway Moxie

Original name Siem Moxie. A walk-to-work Installation Support Vessel (ISV) of the SX163 design, to transport work crews to platforms and foundations to prepare for submarine cable pull-in and terminations. Can support the erection and maintenance of wind turbines once the submarine cable installations are completed.

Built by




Owned by


Designed by

Ulstein Design & Solutions AS

Ordered by

Siem Offshore

Operated by

Seaway Offshore Cables

IMO Number


Principal dimensions

74 m
17 m
Dead weight:
2,835 tonnes
Draught (max):
6.4 m
Speed (max):
9.1 kn
60 POB
Deck area:
200 sqm

Note: Subject to selected variant configuration


Uptime gangway:
Hs up to 3.5 m
Knuckle boom crane:
MacGregor three axis compensated crane
Voith Schneider Propellers:
2 sets
Offshore Support Units (OSU):
Generators, pull-in winches, tools and equipment for personnel life support on the turbine foundations.

Featured solutions

Ship history

IMO Number: 9676216

Designed by ULSTEIN, 'Seaway Moxie' (previously: 'Siem Moxie') is an Installation Support Vessel/Service Operation Vessel developed and purpose-built for the offshore wind sector. With an active motion-compensated personnel transfer gangway, the main services/duties are:

  • Support of installation, repair and maintenance services on fixed offshore structures and other offshore installed assets
  • Safe transfer of personnel from a fixed structure to the vessel and vice versa
  • Safe lifting operations of up to 5 tonnes to and from a fixed structure

With reference to: https://www.seawayoffshorecabl...

The term ‘Walk-to-Work’ originates from the desire to offer offshore personnel the capability to transfer to offshore structures without requiring them first to climb up a ladder or be transferred using a transfer basket on a crane.

'Siem Moxie' was the first of her kind to operate in offshore wind farms in Europe. She was designed and built to allow offshore personnel safe access to foundations and platforms in calm and rough seas. She has proven her worth in the field, making up to 54 successful connections and transfers in a 24 hour period. She has shown that she is able to work in up to 3.5m significant wave heights.

Built at Fjellstrand Verft for Siem Offshore, the 'Siem Moxie' was named in Hamburg on 10 April 2014. E.ON took patronage of the ship after delivery.

“We chose the Siem Moxie because it will make our installation operations extremely safe and efficient,” Sven Utermöhlen, Head of International Offshore business at E.ON, explained.
“In addition it will help make the construction of offshore wind farms more cost-effective, thereby helping this technology move closer to market maturity.”

The 'Siem Moxie' was firstly deployed on E.ON’s Amrumbank West offshore wind farm project north of Helgoland by Siem Offshore Contractors for the installation of the inner array grid submarine cable system. Working in installation support, the vessel is also characterized as an ISV vessel.

Watch film of the 'Siem Moxie' at work.

Offshore Renewables Award

The Siem Moxie was awarded the “Offshore Renewables Awards 2014”. It is the very first X-BOW support vessel which features two sets of Voith Schneider Propellers. Its design drew on a wealth of experience within the offshore business. The Siem Moxie’s low fuel consumption makes it particularly environmentally friendly. The vessel’s key features are a 3D motion-compensated knuckle boom crane and an active motion compensated personnel transfer gangway, permitting the safe transfer of work crews. Thanks to the ship’s active roll stabilization capabilities, offshore works can continue even in challenging sea and wind conditions.

2016: Nordsee One - 'Siem Duo'
Working as part of a 'Siem Duo' in cable installation works on the Nordsee One Offshore Wind Farm (OWF) in the German Bight of the North Sea. The 'Siem Duo' is consisting of the Cable Lay Vessel (CLV) Siem Aimery and the Installation Support Vessel (ISV) Siem Moxie. The Siem Moxie is assisting the CLV for the submarine cable pull-in, termination and testing activities. The vessel's active motion-compensated 'Walk to Work' (W2W) gangway is used to safely transfer personnel to and from the individual foundations in significant wave heights of up to 3 m. In September, three weeks ahead of schedule, the inter-array cables for the wind farm had been installed, as well as the foundations and the offshore substation for the 54 wind turbines.

2016/17: Veja Mate - 'Siem Duo'
Awarded the engineering, procurement, installation and commissioning (EPIC) contract for the IAG cable system of the Veja Mate Offshore Wind Farm. The 67 wind turbine generators of the project are located 115km north of the German coastline within the German Bight sector of the North Sea in water depths of up to 40 metres.

Starting on 1 October 2016, the 'Siem Duo' started the installation of the submarine composite cables. On 6. February 2017 all the 73 inner array grid cables of the Offshore Wind Farm had been installed and trenched 10 weeks ahead of schedule; "The Siem Duo demonstrated its advanced weather operability during the harsh winter season, whereby both the operations of the gangway on the Siem Moxie as well as post-lay trenching by the Siem Aimery were undertaken in significant wave heights of up to 3 m." Mr. Regis Rougier, Managing Director of Siem Offshore Contractors stated: “It is a pleasure to confirm the successful completion of another project ahead of schedule, our third project utilising the “Siem Duo”."

The Siem Moxie assisted with the cable pull-in, termination and testing activities deploying SOC’s dedicated offshore support units (OSU) equipped with generators, pull-in winches, tools and equipment for personnel life support at the individual offshore work sites. The OSUs were transferred using the Siem Moxie’s 3D motion-compensated crane, while the active W2W gangway was used to facilitate the personnel transfers to and from the individual foundations and offshore substation.

From November 2017 - The Rentel offshore wind farm project
The Siem Moxie went on charter to Tideway BV, part of Belgian DEME NV, to support the completion of the inner array grid cable installation scope on the currently constructed Rentel offshore wind farm off the coast of Belgium. At this time, the Siem Moxie had, since launch in April 2014, successfully performed over 14,000 individual connections to offshore structures both during the construction and operational phases, transferring in excess of 54,000 personnel via the in-built active heave compensated gangway in up to 3.5m significant wave height, while further supported by the on-board 3D motion-compensated crane. The vessel has successfully performed a number of ‘ship-to-ship’ transfers as well.

The 42 wind turbine generators of the 309 MW Rentel offshore wind farm project are located 40 kilometres off the Belgian North Sea coast. The offshore wind farm is expected to deliver first power to the Belgian grid by mid-2018, while the entire offshore wind farm is planned to become fully operational by the end of 2018.

2018 - ownership change:
Subsea 7 acquired Siem Offshore Contractors (SOC) from Siem Offshore, to ensure continuation of SOC’s professional services on current and future projects. SOC is part of the Renewables and Heavy Lifting business unit of Subsea 7. The 'Siem Duo' was included in the transaction, and Siem Moxie changed name to Seaway Moxie.

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