Most novice Ironmen and Triathletes have to overcome there fear of the swim (open water swimming), in order to complete there goal race. Some of these tips in the attached article may be of assistance.
http://www.trinewbies.com/tno_swim/tno_swimarticle_04.asp
The Riddle of an Ironman's Life 
Good feedback from Georgie Thomas:
Great article and very much in line with what I would teach at a Total Immersion swim workshops (www.totalimmersionsa.co.za). However, I would maybe differ from the advice on practicing ‘polo swimming’ in preparation. Sighting should be done as ‘seamlessly’ as possible and with least disruption to your rhythm and stroke. Practice in the pool, but practice what you will do in open water – try to lift you head as little as possible so as not to upset your balance, lift as little as the conditions will allow, surf the water with your goggles. Here in PE and in many other venues you can don’t necessarily have to only sight the buoy you can use the cranes in the harbour for example. Practice incorporating sighting into the rhythm of you stroke and don’t be tempted to take an extra breath in the process. Also remember sighting is not the only way to navigate – tune into your internal GPS.