Original Casting Plans Sheds New Light on Sally Field Mystery.

A friend of mine who does film research discovered pre-production documents on "Beyond the Poseidon Adventure". He said there were three actors in the running to play the tugboat Captain.

The first was John Wayne who approached Allen for the role because no one was making Westerns anymore and Clint and a young Arnold S. had all the other action genres covered. He read the script and, not surprisingly, backed out. Irwin Allen's personal choice was Burt Reynolds. He was sent a copy of the script and he too passed on what he thought was going to be a turkey. The third actor in consideration was Clint Eastwood, only because he was WB's leading man and the execs were hoping he'd take the role. After a read, Clint passed on it too.

My guess is that since Sally Field was still an item with Burt during that time (mid '70s) she most likely signed on to do the film with him, but did so prior to his backing out. Irwin Allen is not one known for breaking contracts, so Sally was stuck with doing the movie opposite Michael Caine who wanted more punishment from another Allen-directed film (he did "The Swarm" the year before).