Swimming in open water is HARDER than swimming in a pool. Salt water or not... you have waves to deal with. Not to mention, that it takes more energy to sight... lifting your head every 6 strokes (estimate, some say every 4 if you can't swim straight very well) to make sure you are on track. Not to mention... that some people lose focus and get nervous, when they swallow water when a wave hits... or when they get water up their nose.

When you say you can't swim that long... what do you mean by that? Can you do 750 meters/or yards... without stopping? If not... then I suggest that you think long and hard before jumping in open water.

Now, if you can do a solid 1000 meters/yards without stopping in a pool... and you can do some open water swimming BEFORE the event... then try the tri.

But, make sure you that you are mentally and physically prepared to swim in open water. You need to be OK with swimming in waves... possibly having someone kick your goggles off your face, or hurting you... swallowing water... and spotting the buyos (? spelling) to make sure you stay on course.... being able to face and conquer all those challenges without losing focus on swimming and finishing.

You don't want to be one of the ones pulled out of the swim portion due to lack of skill and confidence.