Open Water 5x400m Race Pace Interval Swim Session

Session Overview

This open water interval session uses 5 x 400m efforts at race pace to build the speed endurance and sighting confidence you need for triathlon swim legs from sprint through to Olympic distance. By swimming at race effort in real open water conditions, you’re training your body to maintain pace while navigating, drafting, and dealing with chop — the exact demands of race day.

What You’ll Need

• Open water venue (lake, reservoir, or calm sea) with buoy markers or swim buddy
• Wetsuit (if water temperature is below 22°C)
• Bright swim cap — always wear one for visibility
• Safety buoy (recommended for solo open water swimming)
• GPS watch with open water swim mode

Warm-Up (5–8 minutes)

Start with 5–8 minutes of easy swimming to acclimatise to the water temperature, especially if swimming in a wetsuit. Include 4 x 25m accelerations to bring your heart rate up gently. Practise sighting during the warm-up — look up every 8–10 strokes.

Main Set

Swim 5 x 400m at your target triathlon race pace, with 90 seconds rest between each effort. Use a buoy loop, a visible landmark, or a pre-measured 200m course swum twice per interval:

• Efforts 1–2: Controlled race pace — RPE 7, strong and rhythmic, focus on straight-line swimming
• Efforts 3–4: Race effort — RPE 8, push the pace while maintaining stroke efficiency
• Effort 5: Best effort — RPE 8–9, negative split where possible, finish strong
• Sight every 8–10 strokes throughout; use the rest periods to note your drift and correct technique

Cool-Down (5 minutes)

Easy swim for 5 minutes, using backstroke or very easy freestyle. Focus on long, relaxed strokes and let your breathing fully recover. Exit the water slowly — open water can cause blood pressure changes on standing, especially after intense efforts.

Coaching Notes

• Never swim open water alone — always use a buddy or tell someone your location and return time
• If conditions are choppy, shorten efforts to 200m and take more rest — open water pace is typically 5–15% slower than pool pace
• Beginners: reduce to 5 x 200m and use effort 1–2 intensity throughout
• Advanced: reduce rest to 60 seconds and aim for consistent splits across all 5 efforts