A bit more history on the gambling boats anchored off Long Beach / Santa Monica, CA --
The SS Rex was anchored in Santa Monica bay, but water taxis provided service to & from Long Beach as well as St. Monica boat docks.

In addition, there were 2 other gambling boats: the SS Tango (of which chips are known) and one other boat (I forget the name, but no chips turned up from it that I know of).

For movie buffs, there's a 1975 film titled "Farewell, My Lovely", starring Robert Mitchum as a 1940's detective, Philip Marlowe. The climax of the film involves going out to a gambling boat a la the SS Rex or Tango. Not a 5-star film, but interesting, as I recall. Of the film noir type, like "Chinatown" if you like that sort of detective movie. It should be out there on DVD if you search for it, though I haven't seen it since its original run.