Pool pace is a useful starting point, but open-water swim pace is not a direct copy of your best repeat in the lane. No wall push-offs, sighting, contact, chop, current, wetsuit fit, and navigation can all move your triathlon swim split.
Start with a repeatable pool pace, then add 5 to 15 seconds per 100 m for open-water conditions unless you have race data that proves otherwise. Use the pace-to-split converter to convert that adjusted swim pace into a race split.
Use repeatable pace, not best pace
Your best single 100 m is rarely a good race input. A better number is the pace you can repeat calmly across a longer set while maintaining form. For example, if you can repeat 10 x 100 m at 2:00 with short rest, that is more useful than one 1:43 effort.
Why open water is slower for many athletes
Open water removes the wall push-off and adds navigation. Every sighting motion can interrupt body position. Contact at the start can raise heart rate. Choppy water can shorten the stroke. These small costs add up across 750 m, 1.5 km, 1.9 km, or 3.8 km.
When open water can be faster
A wetsuit, legal drafting, current, and strong course navigation can make open-water pace faster than expected. Experienced swimmers sometimes gain time from better body position and drafting. Newer swimmers should still plan conservatively until race data supports a faster estimate.
Simple adjustment guide
- Experienced open-water swimmer: pool pace plus 0-5 sec/100 m.
- Average age-grouper: pool pace plus 5-10 sec/100 m.
- New or anxious swimmer: pool pace plus 10-20 sec/100 m.
The fastest overall race rarely comes from forcing the swim. A calm swim sets up a cleaner T1, a steadier bike, and a run that begins with less stress already in the system.