3km Open Water Endurance Swim

Session Overview

This 3km continuous open water swim is designed for advanced triathletes building towards 70.3 or IRONMAN distance events. You’ll develop sustained pacing, breathing rhythm, and the mental focus needed for long-course racing in open water.

What You’ll Need

• Wetsuit (recommended for UK open water temperatures)
• Open water safety swim buoy (mandatory for solo swims)
• GPS watch with open water mode
• Swim buddy or lifeguard-supervised venue

Warm-Up (15 minutes)

Enter the water and swim 400m easy at conversational pace. Focus on settling your breathing and adjusting to the water temperature. Practise sighting every 8-10 strokes to establish your line early in the session.

Main Set

Swim the following set at a sustained aerobic pace, aiming for RPE 6/10 — challenging but maintainable over the full distance:

• 1 x 1500m at steady Zone 2 pace (RPE 6), rest 2 minutes
• 1 x 1000m at slightly elevated Zone 3 (RPE 7), rest 90 seconds
• 1 x 500m at strong race-effort Zone 3-4 (RPE 7-8)

Cool-Down (10 minutes)

Swim 200m easy backstroke or breaststroke to fully lower your heart rate. On exit, stretch your shoulders and lats for 5 minutes to prevent post-swim stiffness.

Coaching Notes

• Sight every 8-10 strokes using a two-breath technique to avoid veering off course
• Avoid starting too fast — the first 500m should feel almost too easy
• Scale down: if 3km is too far, swim 2 x 1000m with a 3-minute rest instead
• Heart rate target: Zone 2-3 (65-80% max HR) for the majority of the session