This is for Dave Roberts:

68:19 for 4000yds. This is pace for a 72 minute Ironman swim. Not a lot else to say, -0.2% decoupling is not bad. Effort certainly did drift up. Started out paying attention to Jan in the next lane, not bad to start out a bit hard, that’s how it goes on race day too so I don’t mind doing it in practice. My watch wasn’t running correct so I needed to fix it after 500m. I felt quite smooth from 750m through about 2000 and then needed to concentrate quite hard. Variability in pace reflects this, dialed in well early on, gets a bit shaky and then control is regained once I switched counting “up” to counting “down” and pace is excellent to finish off.

The trendline is a per-kilometer average pace.