Indeed he did. See his ET biography. Come across as a brave and selfless man. RIP.
Reading about Martin Gallagher, I wonder if he was the unidentified man who helped Kate Gilnagh and firend when they got lost trying to find a way to the boat deck. The incident is described in page 97 of Walter Lord's A Night to Remember and a few other works. Apparently Kate and her companion got lost and ended up in a Second Class area where an unknown man standing in the shadows helped them onto the deck above by asking them to climb onto his shoulders holding the railing for support. Both young women survived but were unable to identify their saviour. Reading about the way how Gallagher helped the others through the Second Class areas suggests that he might have been that man.
Martin Gallagher appears to have been quite active in helping others. As mentioned above, he helped Mary Glynn, Julia Smyth, Kate Connolly and Margaret McGovern towards Lifeboat #13 on the starboard side. Earlier, he had helped Ellen Mockler, Margaret Mannion and 'other Irish girls' get into Lifeboat #16 on the port side; since Kate Gilnagh was also rescued on #16, there is a very high chance that the man who helped her in the semi-darkness was indeed Martin Gallagher.