Found a great article on the actual events that unfolded at Dunkirk:
http://www.dailymail.co.uk/news/art...vacuation-Dunkirk-recalled-minute-minute.html
It's interesting to note that Mark Rylance's character Mr. Dawson was based on an actual real person. That person was retired Royal Navy Commander Charles Lightoller. Lightoller was famous for being the second officer of the Titanic and was the highest ranking officer to survive its sinking in 1912. He served in the Royal Navy during WWI and the ship he commanded sank a U-boat in 1918. In 1940 he was retired but answered the call and took his personal yacht, the "Sundowner," over to Dunkirk.
Here are the excerpts from the article on Saturday, June 1st which can be spoilers for those that haven't seen the film:
I also found this article which gave a little more info about that day and the Sundowner which is now in a maritime museum in England:
http://www.adls.org.uk/t1/content/sundowner-0
Lightoller is a legend, he survived the Titanic, he survived naval combat with Germans in WWI, he survived being strafed by German aircraft while trying to rescue soldiers in WWII, he lost his youngest son who was in the RAF during the first week of WWII and he lost his oldest son, who helped him sail the Sundowner to Dunkirk, in the last year of the war. Now he was fictionally immortalized in this film after being non-fictionally immortalized in multiple films on the Titanic. Really great history.