How Luthor Came to Hate Superman
Probably the most important milestone in Superman's career was his first 'reboot' by John Byrne in 1986. This series is the best Superman origin/early adventures story ever written and drawn. John Byrne was at the top of his game both as a writer and as an artist after producing a decade's worth of quality material for Marvel.
In the fourth issue Clark and Lois have a work/date attending a party aboard Lex Luthor's luxury ocean liner 'Sea Queen'. First Lois gets into a tiff with Luthor, then armed terrorists take control of the boat and toss Clark overboard.
Aside from the brief fight with the terrorists, there isn't much Superman action in this issue (though he does rush a woman in labor to a hospital toward issue's end), but it's more about building characters, specifically Clark and Lois' relationship, Lois and Lex's relationship, and the new enmity of Luthor and Superman.
If you want to jump into Superman for the first time - this six issue mini-series is your best choice.