Share 'Alternate Swimming Sessions'

Hi There, My Ironman is at April 2010. My Swimming ability is poor and I find the swimming sessions in the plan too hard for me. Since the IM is so far away and the ROI of swimming is very low I'm thinking of changing the swimming parts of the plan. So instead I'm doing 2 GYM sessions and I want to add 1-2 short swimming sessions just to build it up slowly. Any suggestions of how should those s...