The next question is whether to line up on the inside, middle or outside. Some triathlons, especially the sprints, will have a rope/line going out the length of the swim instead of buoys. Against the rope would be considered the inside. If his wave is a large group of triathletes going off together, he could get stuck between the rope and the swimmers in front and beside him unless he is able to go out fast and get ahead of the pack. If it is marked with buoys only, you're still supposed to stay to one side of them. While he may not get stuck between a rope and swimmers, he could still get pushed "inside" and end up having to go around the buoy in a straight line portion of the swim.

If it is an out and back swim, he'll have one 180 degree turn where he'll have to almost stop to turn if he is onthe extreme inside. Regardless of a 90 or 180 degree turn, if you're on the inside you may feel the pressure of swimmers against you as you turn unless you're at the head of the pack.

I suggest that he lines up in the middle to outside half of the group. The faster swimmers will go out and then get to the inside. As they move in, he can move in with them and draft. He'll be less likely to get trapped between other triathletes. When he gets to the turn, he may have to swim a little farther but he can maintain his rhythm better and won't feel that pressure. If the 400m swim is out and back and he lines up 20m to the outside, he will only have to swim around 2m farther for the entire race as compared to someone that lines up to the extreme inside. That 2m is worth the comfort and lack of congestion at the beginning of the race. Another benefit to lining up to the outside is that he may not have to go out as fast (anaerobic) to claim his position in the pack and that can help him finish stronger in the 2nd half of the swim.