Hugill was a deck singer, not a pop singer.

When Alexander Blue of Greenock sang (for James M. Carpenter), "Have you been in Rio Grande?" he pronounced it as "Ry-o Grand."

Joanna Colcord, who "grew up at sea" in the '90s (her father was a captain) wrote in 1924 that "the American sailor disdained any other pronunciation than 'Ry-o.'"

On the other hand, few collectors commented on it. So plenty of sailors must have sung "Ree-o" too.

Just don't do it in front of an audience of overaged folkies.