5 mile swim workout plan

I would very much train like running a marathon -- the most important part as far as I understand marathon training - gradual consistent long "runs" for you swims - ideally one every week, maybe start one every 10 days - work your other workouts around that long swim. Goal is guessing about 3.5 hour range - you should be near there about 2 weeks prior to meet. Build a simple plan - 90 min long swim now - add in 2-3 60 min swims.  Next week 95-100 min -- and so on -- if a week is a struggle - keep at that level - body needs time to adopt... 

I would also add support work - thats a long swim - lot of arm rotation - get some habit of solid stretching and shoulder support strength - them muscles that we don't use in swimming. 

I would very much train like running a marathon -- the most important part as far as I understand marathon training - gradual consistent long "runs" for you swims - ideally one every week, maybe start one every 10 days - work your other workouts around that long swim. Goal is guessing about 3.5 hour range - you should be near there about 2 weeks prior to meet. Build a simple plan - 90 min long swim now - add in 2-3 60 min swims.  Next week 95-100 min -- and so on -- if a week is a struggle - keep at that level - body needs time to adopt... 

I would also add support work - thats a long swim - lot of arm rotation - get some habit of solid stretching and shoulder support strength - them muscles that we don't use in swimming.