In any case, here are websites that you may find useful in obtaining additional information about the ships in which he served.
http://www.shipbuildinghistory.com - Shipbuildinghistory.com provides basic information about where and when ships were constructed: the shipyard name and location, dates, subsequent fate of the ship, including name changes, and other information. The Search option is found at the bottom of the home page. Note that this site contains records for many thousands of ships, some of which had identical or similar names, so in some cases identifying the correct ship may be a challenge.
Of the three ships above:
TRISTAN is found at http://shipbuildinghistory.com/shipyards/large/greatlakes.htm, hull no. 84. Note that this ship, originally named PENOBSCOT, was built in Ecorse, Michigan, just downstream of Detroit on the Detroit River, in 1911. A rather small ship, presumably she was sent through the Welland Canal soon after construction to operate in the Atlantic.
JOHN MARY ODIN is found at http://shipbuildinghistory.com/shipyards/emergencylarge/toddhouston.htm, hull no. 67.
WILLIAM EUSTIS is found at http://shipbuildinghistory.com/shipyards/emergencylarge/toddhouston.htm, hull no. 38.
For Liberty ships only, see http://www.mariners-l.co.uk/LibIndex.html for additional information about a given Liberty ship. You will have to search by eyeball to find the correct range of names for the ship(s) in question. Note that the alphabetical list of ship names is by FIRST name of the ship, a traditional way to alphabetize the names of ships.
Similarly, for Victory ships, if you find that your father served aboard any, see http://www.mariners-l.co.uk/Vicindex.html. And for class T-2 tankers, if any, see http://www.mariners-l.co.uk/T2.html.
http://www.convoyweb.org.uk/ - ConvoyWeb is an excellent resource for tracing the movement of ships in convoy during World War II; in particular see http://www.convoyweb.org.uk/hague/index.html. On the latter page you can perform a Ship Search to search for any ship by name. Results will identify the convoy(s) in which a ship sailed, origination port, destination port, and inclusive dates. There may be some additional information about individual ships in a convoy (sometimes including cargo) or additional information about the convoy as a whole. There will be no information about crews. At the bottom of each page of results you will find a statement, “To continue the search for OTHER voyages of [name of ship], click here.” Following this link will provide information in chronological order about the ship in question throughout her wartime career, including those occasions in which she sailed independently, i.e., not in convoy and without warship escort.
A similar website, although generally less comprehensive, is http://warsailors.com; the search box is near the top center of the home page. Although the site concentrates on Norwegian merchant ships during World War II (and the site is in English), it broadly covers many convoys and many ships, similar to ConvoyWeb. On occasion, WarSailors.com will provide much greater detail on a given ship or for a given convoy than ConvoyWeb.
https://uboat.net/ - UBoat.net has information about many Allied ships that had the misfortune of encountering German U-boats, whether sunk or damaged. The site also contains information about the activity and fate of each U-boat. There is a search box on the right side of the home page to search for information such as ship name, U-boat number, or convoy number. For example, information about the attack upon and loss of WILLIAM EUSTIS is found at https://uboat.net/allies/merchants/ship/2796.html and https://uboat.net/allies/merchants/crews/ship2796.html; the latter page lists your grandfather and indicates that he (and indeed the entire crew) was rescued after their ship sank. UBoat.net has photographs of many of the ships attacked by U-boats but not, unfortunately, that of WILLIAM EUSTIS.
http://www.usmm.org/ - This site, American Merchant Marine at War, contains voluminous information about the merchant marine in general, specific ships, list of merchant marine and Armed Guard casualties by name (both deaths and injuries), lists of ships damaged or sunk (including dates, locations, cause, and casualties) and vast amounts of other information. Unfortunately, the site is fairly difficult to navigate. Here are particularly useful pages:
http://www.usmm.org/sunkaz.html - Alphabetical list of U.S. merchant ships sunk or damaged in World War II.
http://www.usmm.org/ armedguard.html - List of Armed Guard killed or wounded in World War II.
http://www.usmm.org/casualty.html - List of U.S. merchant mariners killed or wounded in World War II.
http://www.usmm.org/ww2.html - General information about the U.S. merchant marine during World War II.
To address one of your specific questions:
http://www.usmm.org/photosource.html - Sources of photographs of U.S. merchant ships. Unfortunately for you and others, the second source on the list, Mr. William Hultgren, recently died. It is unfortunate in that his collection of photographs concentrated on photos of Liberty ships, probably the most comprehensive private collection in existence. (As someone who knows his way around a darkroom, I would love to know what has become of his collection.)
Of the other sources, the Mariners Museum in Newport News, Virginia, may be promising. I have visited the museum library and searched through its catalog of ship photos, which is quite extensive. You can make an online search to see whether the museum’s collection includes a photo of a given ship at https://www.marinersmuseum.org/library/#photography_collection; the link to the search is at the bottom of the page.
Likewise, the Library of Congress in Washington, DC, and the National Archives facility in College Park, Maryland (just outside DC), may be particularly helpful. I have no personal experience with the Library of Congress but I have visited the National Archives’ College Park campus, where one can search in person and without charge for information. Absent a personal visit, it may be possible to obtain research assistance from Archives staff, for a fee.
My understanding is that the U.S. Coast Guard took many aerial photographs of merchant ships leaving port during World War II, a kind of mug shot of each ship. I am uncertain where that collection of negatives may reside, possibly with the National Archives. Since the original photographs were taken by an agency of the federal government, all such Coast Guard photographs are in the public domain.
Other possible sources of photographs of World War II-era merchant ships include the following:
Information about merchant ships other than Liberty, Victory and T-2 tankers, particularly older ships, can be difficult to find online. With careful searching I found information about TRISTAN (constructed as PENOBSCOT, later sold and renamed, in order: P.L.M. 2 *, LAIRG, TRISTAN (between 1928 and 1949) and finally LEPUS, her name when she sank in 1956.
(* P.L.M. was a French railroad company that operated between Paris, Lyon and Marseilles. The company established its own fleet of ships to transport coal from England to France. The company unimaginatively named its ships “P.L.M.” followed by a number.)
Therefore, for detailed information about this ship, under its various names, see https://greatlakes.bgsu.edu/item/438529 (with a photograph of her while named PENOBSCOT), and https://www.greatlakesvesselhistory.com/histories-by-name/l/lairg. You’re welcome.
I hope the above information is useful.
Ron Carlson, Webmaster
Armed Guard / Merchant Marine website