JONATHAN RABAN, the British author who in his new book, Old Glory: An American Voyage (Simon and Schuster) traveled the length of the Mississippi by boat, obviously has been struck by maritime fever. He's back in London, buying a boat to explore the coast of England, pirate coves and all. The book that will come out of the voyage, scheduled to last a year, is tentatively called Foreign Land. . . . Some of the attention that's been going to Ted Mooney's novel Easy Travel to Other Planets should be siphoned off to Rob Swigart's The Book of Revelations (Dutton). Both have heroines who become intimately involved with dolphins. In fact, there's a boom this season in cetacean books: also being published are Jeremy Lucas' Whale (Summit) and Robert Siegel's Whalesong (Cornerstone Books); in the works at Random House is a novel called Soundings by Hank Searls. . . . Authors are a dime a dozen on television but usually they're calling attention to themselves. Not Edward Jay Epstein (Inquest, Legend, the upcoming The Diamond Invention (Simon and Schuster)), who had an utterly anonymous bit part in a Saturday Night Live Jack Abbott send-up, titled "Prose and Cons." Epstein played one of the literary agents trying to sign up prisoners with best-seller potential. . . . Senators' wives are sending each other copies of Marilynne Robinson's novel, Housekeeping (Farrar, Straus and Giroux). Published last winter, it received unanimously favorable reviews, but fans like Barbara Pryor (Sen. David H. Pryor, D-Ark.) and Molly Boren (David L. Boren, D-Okla.) are winning it new readers by sending out copies as gifts. . . . Watch this space for news from Tom Congdon, once of Congdon & LattMes, now of Congdon & ? The "?" is because Jean-Claude LattMes, the French money man for the firm, has joined French publisher Hachette and will return to Paris. Congdon looks to have a hot book on his hands in Joan Barthel's A Death in California. . . . Is Fawcett's vice president and publishing director Leona Nevler chafing at the CBS bit? . . . . Carole Baron, vice president and editor in chief at Crown who held Judith Krantz's hand for Princess Daisy, is going to Dell- Delacorte to replace the departed Ross Claiborne, vice president and editorial director.