Cardiff Mariners  and  Swansea Mariners provide access to a database of mariners and a register of ships from Cardiff and Swansea. Much of the information is about earlier periods, but there is some First World War information and if you want to find out about the history of seafaring in a family this is a useful site. There is also a host of other material such as photographs of ships and ports.

Welsh Mariners an online database with details of over 23,500 Welsh Merchant Mariners – masters, mates and engineers. Again, the period covered is earlier than the First World War but may be of use if you want to discover more about the history pf seafaring in a Welsh family.

Rhiw.com is a website which includes information on all aspects of Llŷn and the sea, including information on local ships and mariners, including in the war period.

Amlwch Data has databases for mariners from Amlwch, the ships they sailed on and their fate. It contains information on the war period and includes other material such as photographs.

The Heritage and Cultural Exchange – Tiger Bay & the World has a searchable database of information about Cardiff ships of the First World War, it also hosts photographs collected from the Butetown community over the past few decades.

Find My Past website hosts a wealth of transcriptions and scans of original documents, including many sets of records digitised from the collections of the National Archives and local record offices.  These include naval and merchant service records, deaths at sea records, baptism, marriage, burial and census records (especially the 1911 census) which will tell you about an individual and their family and where they were living shortly before the war.

Local libraries and archives in Wales have a subscription, so you can view records there for free. If you are using the site at home, you will be able to carry out searches but will need to pay to view records.

Commonwealth War Graves Commission website hosts a database of those who lost their lives in the First World War. A search on this database can be refined by service, rank, ship and place of birth. It will tell you where the individual is commemorated and, if buried, the details of the grave.

Uboat.Net a website dedicated to the U-boat wars of the First and Second World Wars. This site has carried out extensive research on thousands of ships and U-boats. If you know the name of your ship, put that into the search bar in the link. This will give you a page showing the location of where the ship was sunk and clickable links to more information.

Wreck Site is the world’s largest online wreck database that includes wrecks of the First World War. It incorporates technical information on the ships and often includes images, dive reports and casualty details.

Dreadnought Project is a naval history wiki focusing on naval history between 1880–1920 and has articles on 8300 naval personnel and 5000 ships, including ship’s plans. It has produced a series of 3D simulations and has a good resources page.

Naval-History.Net a comprehensive website with a section on the First World War, which gives in-depth information on the history of the War at Sea, often with original sources. It has sections on the Navy, the merchant service and the U-boat war and includes medal lists.

Pastscape Historic England’s online database of English sites. The advanced search allows you to define by ‘WRECK’ of the ‘FIRST WORLD WAR’ which brings up over 3000 results.

Royal Museums Greenwich website has links to the information on ships and crew of the merchant service and Royal Navy in the First World War, which is held by the Greenwich Maritime Museum’s Caird Library and Archive.

Royal Navy (RN). See guides to commissioned officers, warrant officers and ratings up to 1928 and 1928 onwards.

Royal Naval Reserve (RNR) – professional seafarers who served with the Merchant Navy and who could be called to serve in the event of war. See The National Archives guide.

Royal Naval Volunteer Reserve (RNVR) – civilians who volunteered to train on shore-based establishments and then at sea, who could be called to serve in the event of war. Most officers recruited during wartime were granted temporary commissions in the RNVR. See The National Archives guide.

Abbreviations in merchant seamen’s records. See A guide to abbreviations used in merchant seamen’s records.

Lives of the First World War a website created by the Imperial War Museums (in partnership with Find My Past) to be a permanent digital memorial to the people who served in the First World War. It is populated with nearly eight million names of men and women; members of the public are needed to build these ‘Life Stories’ by adding images, stories, and adding facts. The site will remain live and active until 18 March 2019 then it will remain permanently available as an online resource.

Jutland Crew Lists Project is compiling, with the help of volunteers, searchable databases of those who served on ships that were active at the Battle of Jutland in May 1916. Original hand-written records in The National Archives are transcribed to create searchable lists of those that served, died or were wounded in this battle.

The Great War 1914-18 – a guide to British Campaign Medals of WW1 – this site gives detailed information on the types of medals awarded, what they were awarded for and clear colour photographs of the medals.

Archives – local

• Anglesey Archives
• Bangor University Archives
• Carmarthenshire Archive Service
• Ceredigion Archives
• Conwy Archives Service
• Denbighshire Record Office
• Flintshire Record Office
• Glamorgan Archives
• Gwent Archives
• Gwynedd Archives, Caernarfon & Dolgellau
• Pembrokeshire Record Office
• Powys Archives
• West Glamorgan Archive Service, Swansea
• Wrexham Archives and Local Studies Service

Welsh museums with maritime collections

• Amgueddfa Forwrol Llŷn Maritime Museum
• Barmouth Sailors Institute
• Museum of Cardiff
• Carmarthenshire Museums
• Ceredigion Museum
• Conwy Museums
• Friends of Newport Ship
• Haverfordwest Museum
• Holyhead Maritime Museum
• Milford Haven Maritime Museum
• Newport Museum
• Oriel Ynys Môn
• Porthcawl Museum
• Porthmadog Maritime Museum
• Swansea Museum
• STORIEL, Bangor
• Tenby Museum
• Tiger Bay & the World
• VC Gallery
• Waterfront Museum, Swansea
• West Wales Maritime Heritage Society museum

Tracing your Merchant Navy Ancestors: A Guide for Family Historians, by Simon Wills (Pen and Sword Family History, Barnsley, 2012)

Tracing your Naval Ancestors: A Guide for Family Historians, by Simon Fowler Wills (Pen and Sword Family History, Barnsley, 2011)

My Ancestor was a Merchant Seaman, by C T and M J Watts, (Society of Genealogists, 2002)

Women in the First World War, by Neil Storey and Molly Housego (Shire Publications, Oxford, 2010)

The Fleets Behind the Fleet: The Work of the Merchant Seamen and Fishermen in the War, by W. MacNeile (Dixon, Hodder & Stoughton, 1917)

The Merchant Navy by Archibald Hurd, published by John Murray, London, 1921–29 (3 volumes). This official history of the Mercantile Marine in the First World War can be viewed online on the Naval-History.Net website.

Growing up among sailors, by J Ivor Davies (Gwynedd Archives Service, 1983)

Black Salt: Seafarers of African Descent on British Ships, by Ray Costello (Liverpool University Press, 2012)