We were two boats passing in the night," says Nadine Louviere, and she isn't taking poetic license. Louviere, 37, from Wisner, La., is a cruise director on a Mississippi steamboat, the Delta Queen. Her boyfriend, David Evans, 26, from Auburn, Ala., is a musician on another steamboat, the Mississippi Queen. Since meeting in October 1986 the couple has had many a river to cross. Their boats are usually not in the same place at the same time, which meant the lovers hardly saw each other and had to court by ship mail. They waved to each other as their paths crossed and vacationed on each other's boat. I've only spent two nights in my apartment since June," says Evans. When the boats made a rare joint appearance in Natchez, Miss., last month, Louviere and Evans decided to take advantage of the situation. They staged a romantic steamboat wedding on the Delta Queen, watched by several hundred spectators and performed by a nervous Judge Rusty Jenkins (it was his first ceremony). The couple embarked on a six-week honeymoon in Australia and New Zealand—spending most of their time on river cruises.