The pirate way is to swim a bit, bike a bit and run a bit...
Swim can be 30mins - 1 hour
bike can be 70mins - 2 hours
run can be 35 mins - 1 hour....
all depending on speed - fitness etc....
If you are fit,just turn up and do it - you will survive, (as long as you can swim)
Otherwise, get a wetsuite, do an open water swim day somewhere.. and go swim once or twice a week.....
ride as much as possible, (but make sure you can ride 40k)
run - you should have run 10 k at some point