Open Water Swim: 5x600m Threshold Intervals with Sighting Practice

Session Overview

A threshold-effort open water session that builds the ability to hold race pace for extended periods while keeping your sighting sharp — ideal for intermediate swimmers preparing for 70.3 or Ironman-distance swim legs where course drift adds up fast if you’re sighting poorly.

What You’ll Need

• Wetsuit or swimskin (water temperature dependent)
• Tow float for visibility and safety
• Goggles suited to the light conditions (tinted for bright sun, clear for overcast)
• A visible landmark or buoy line to sight against

Warm-Up (10 minutes)

400m easy swim mixing freestyle with a few lengths of breaststroke to settle into the water, followed by 4 x 50m building from easy to moderate effort with 15 seconds rest between each.

Main Set

The core of this session is sustained threshold effort — roughly the pace you could hold for a 70.3-distance swim if pushed — with a deliberate sighting focus on every rep.

• 5 x 600m at threshold effort (comfortably hard — you should finish each rep breathing hard but in control)
• Sight every 6-8 strokes on each rep, picking a fixed landmark rather than the buoy directly ahead of you
• 45-60 seconds rest between reps — enough to reset technique, not enough to fully recover
• On rep 4, practise sighting into low sun or glare if conditions allow — race mornings rarely offer ideal visibility

Cool-Down (10 minutes)

300m very easy swim, focusing on long, relaxed strokes and controlled breathing to bring your heart rate down before exiting the water.

Coaching Notes

• Sighting should cost you as little rhythm as possible — a quick forward peek on the same breath cycle, not a full head-up stroke.
• Common mistake: sighting too often early in a race out of nerves, which burns energy and breaks rhythm. Use this session to build trust in your line.
• Scale down: reduce to 4 x 400m if you’re newer to open water or the venue has limited space.
• Target RPE 7-8/10 for the main set reps — hard enough to be honest training, not an all-out time trial.