Fishing Up North

Bob and Jim always took holidays together. So this year Bob asked "Where do you want to go this year"? Jim said "I'd like to go south this year how about you"?
Bob said "I'd like to go North this year" so they decided to have separate holidays this year.
When they got back they told each other where they had gone. Bob said as you know I went North and found a gorgeous lake, spring fed and mountains in the background. I went swimming, boating and fishing and had a wonderful time, how about you Jim?
Jim said I was walking down the hwy and found some railroad tracks so decided to follow them and see where they went. I got a mile down the tracks and I found a women tied to the tracks. Bob asked "what did you do"? Jim said "I untied her and then had the best sex I ever had with a women". Bob asked "What did she look like"?
Jim said " I don't know I never did find her head"