Finding a teammate who has a similar mindset (do your goals align) and similar pacing will make a huge difference in whether you have an enjoyable experience in swimrun.
Not a bad idea to list out your running and swimming paces as follows:
Half marathon total time or pace per mile on a long tempo run and
Half Ironman or Ironman swim time or pace per 100yd.
The Maine course is getting longer in 2018.
Long Course: 4.25 miles of total swimming, 20.25 miles of running over 11 islands (20% longer than '17)
Short Course: 2.50 miles of total swimming, 10.75 miles of running over 6 islands (50% longer than '17)
Lars Finanger
Odyssey SwimRun