For many triathletes, the swim is the most intimidating element of long-distance triathlon.

The Ironman 2.4-mile swim can be intimidating if you haven’t done the right prep with swim training. These are the four few key Ironman swim workouts I personally like for prep — I also give these workouts to my athletes to test their readiness and build swim confidence, so they feel prepared to nail their swim on race day. Here are a few of my favorite Ironman swim workouts:

Ironman Swim Workout: 400 Repeats

There’s something about 400s that I love – they’re short enough that you can push the pace and they go fast mentally, but they’re also long enough that endurance gets worked and you can easily tap into the Ironman effort and pace. Depending on the athlete’s level of experience, I will start them with 4 or 6 x 400s and over the weeks of training, build them to 10 x 400s by the time we are at peak Ironman training. The 400s are done at goal race pace or slightly faster, with only 15 seconds rest. (Or you can do them on an interval that provides 15 seconds rest). I like the interval option since it’ll encourage you to hold the same pace through all 10 x 400s. If you’re completing the 400 on 5:30, you’d leave on the 5:45 interval; if you start slowing down, you get less rest!

Ironman Swim Workout: Continuous Swims

These can be done in open water if you have that option, or in the pool if open water isn’t available (or if you’re training for an early-season Ironman). If done in a pool, you can do something like 2 x 1800s at race pace with 2:00 rest. If swimming in open water, you can swim 4200 continuously at goal race pace. If you have buddies who can swim beside you, you can practice bumping elbows and also drafting off the hip to simulate a race scenario. With either option, be sure to practice sighting and get comfortable with the rhythm of sighting in your stroke. This workout might be a little boring, but it’s super race-specific and great prep!

20 x 100s at Threshold Pace with 10 Seconds Rest

Ok, maybe this isn’t Ironman specific pacing, but this is a great one for developing confidence and mental toughness, as well as pushing your threshold up a little higher. Again, ideally you’re doing these on an interval that provides 10 seconds rest, so if your threshold pace is 1:15/100, you’re leaving on the 1:25 interval. Your goal is to maintain the same pace throughout all 20 x 100’s. (Your threshold pace should be determined with a swim assessment, I like using 3 x 300’s at best sustainable effort with 20 seconds rest. The average 100 pace of the 300’s is your threshold pace.) Depending on your or your athlete’s level, you can end with an aerobic pull set after finishing the 100’s to make this closer to a 4k swim, building endurance and strength on tired arms.

Pace Changers

This swim can simulate the pace changes you can experience in the Ironman swim, with the quick start to get your position and pick-ups around buoys. Warm up with 300 choice, then go right into the main set (400 steady pull with paddles, rest 15 seconds, 4 x 100 mod hard, rest 5 seconds, 4 x 50’s hard, rest 5 seconds) repeat 4x and rest 3min between sets. Cool down with 200 choice.

These workouts can all be modified to the level you are currently at by decreasing the number of intervals or length of intervals, and also by increasing rest time. I hope these workouts help you crush your next Ironman swim so that you can exit the water feeling fresh and ready to bike! Happy training!

This article originally appeared at Trainingpeaks.com.

Lindsay Zemba Leigh is a USA Triathlon and Training Peaks Level 2 coach. She’s also a certified strength and conditioning specialist and certified nutrition coach.