When doing triathlons, a lot of triathlons are done in open water. It's important to know where you are the whole time so you don't get off track, and you can finish your race successfully and properly.
One good technique for triathlon swimmers is sighting. You want to be able to bring your head out every 3 strokes as you're doing your freestyle, and sight to see where you are. Sighting also allows you to take a breath and help you to orient yourself; where you are in the race and where you are in the open water. A good way to sight is by popping your head outside the water every 3 strokes when doing the freestyle.
You would start off with swimming freestyle, and on the third stroke or fifth stroke or so, you want to keep it in rhythm, you pop your head out to take a breath and also to take a quick look around where you are, and then bring your face back in and continue. Another great technique for triathlons is keeping your head right on the surface of the water so it's easier for you to bring your head out to see where you are. You're wearing goggles when you're doing the triathlon, so when you keep your head right at the surface, you can see where you are in the water. Then having the sighting technique is a great addition to your triathlon race.
Those are some triathlon swimming techniques.