Possible Clues:

• As was Molly Brown, tanning in bleak sun
• Like something that can't be put down, in a way
• Always remaining afloat
• With 88-Across, 1960 musical partly about the 63-Across, with 'The'
• The Titanic's claim to be lacking power outside Belfast, for example
• Tragically inaccurate adjective of 1912