My 2ps worth...
- Big bubble bubble wrap under bottom. Change every 5000m at least.
- Drink lots of water - learn to row one handed and slug a gulp with the other hand.
- Base it on heart rate NOT split. I will go for 130HR next time. Both marathons I did I tried for a split and died after 2.5 hours which is a bit demoralising and painful for the last half hour.
- Eat bananas. I tried eating minstrels but my tooth shattered whilst crunching one in FM2 after 32km. Very disconcerting but I had to carry on didn't I!
- Nothing prepares you for your first one. You can do 2.5 hour rows in preparation but the marathon itself still seems a very, very long way when you do it. (Let alone 50km every day for four days!)