I row six or seven days a week, 20-30 minutes, zone 2 a lot and intervals twice or thrice a week. I’ve been able to maintain my weight loss (80+ pounds) between rowing and diet.

I learned on vacation a couple of years ago that just treading water in the pool at the hotel we stayed at in Ocean City, NJ, burns plenty of calories. It beats rowing, in fact, according to my Apple Watch. Summer 2023, I worried about gaining weight on vacation. Last summer? Not so much.

Having opened the pool, I wondered if I might supplement my morning row with a swim. And wondered too if swimming in our humble backyard tub would compare to the more spacious in-ground pool in OCNJ. So I tried it this morning: I swam in the pool, doing breaststrokes and backstrokes and making four-foot-deep dives to the bottom, swimming from side to side.

I checked Apple Health after and it reported a decent burn for a pretty chill dip in the pool. I compared this to a couple of different rowing sessions: an easy recovery piece and a hard 2K.

Activity	Duration	Intensity	Active Calories	Source
Rowing	30 minutes	Easy	167	Apple Health
Rowing	2k (8 mins)	Hard	127	ErgData
Swimming (backyard)	30 minutes	Easy	354	Apple Health

I added the fifth column, Active Energy, because different apps report different data. Apple Health differentiates between the energy you burn by exercising and what you’d burn just being. ErgData, on the other hand, combines them. I take this to mean that the calorie expenditure reported by ErgData is exaggerated. Concept2’s Calorie Calculator bears this out. In looking into this, I read that some swimming apps report the same way.

I’m circumspect about losing meters this season, having logged 2 million meters during each of the last two years. But: it’s nice to have a low-impact and efficient alternative, if just for a short season.