Swim 1: Build up distances slowly; aim to do around the 750m you will be covering in the race. Break it down into smaller distances - try 100m warm-up swim, 4x50m fast swim 2x100m easy swim, 200m fast swim, 100m easy swim to cool down.
Swim 2: Continue to build up distances - you want to be able to comfortably swim at least 1,000m before the race so the distance doesn't faze you. Swim 5-10 sets of 100m with 30 seconds' rest between each effort.
Swim 3: Introduce some speed into your swim sessions - try on your wetsuit and try to swim in open water. Speed sessions consist of short efforts with long rests - 100m warm-up followed by 10-15 sets of 50m, alternating each effort as fast/slow. Recover for double to triple the time it takes you to do the fast efforts. For example, if it takes 1 minute to do your hard 50m then you should have 2-3 minutes' rest. Try to maintain your form throughout. After a session get out fast and get your wetsuit off as quickly as possible.
Swim 4: Continuous swim for 10-15 minutes; build up by 5 minutes each week.
Swim 5: 100m swim warm-up. Then, 3x200m with 20 secs rest, 2x100m with 30 secs rest, 2x50m easy.
Swim 6: 100-200m warm-up swim, then 5x100m alternating easy (then 20 secs rest) and flat out (30 secs rest); then 5x100m alternating flat out (30 secs rest) and easy (20 secs rest).
Swim Taper: 100m warm-up, then 5x50m as: hard 25m, easy 25m with 40 secs rest, 10x25m flat out with 30 secs rest between each, 100m easy swim. Practise removing your wetsuit.