Sea swims and the cheapest points in the app

The highest rate in the app

Cold water or a sea swim is worth +14 points per hour - the most of any activity Goodday tracks, ahead of vigorous exercise at +12 and time with friends at +11. It is also capped at 45 minutes, so one good swim is the maximum the day will credit.

That combination is deliberate: high reward, small dose.

What the research says

Cold-water immersion has been studied as a treatment for depression and anxiety, with a small number of trials showing meaningful improvements in symptoms (Massey et al., BMJ Case Reports, 2018). Laboratory work has shown that cold-water immersion raises noradrenaline and dopamine - the chemicals involved in alertness and motivation (Sramek et al., European Journal of Applied Physiology, 2000).

So the mechanism is plausible and the early results are encouraging. What we do not have is a large trial proving a daily sea swim prevents depression. Goodday scores it highly because the evidence points that way, not because it is settled.

Why it earns so much in a day-scoring app

The point of a swim is not the swim. It is that you did the thing you did not want to do, in the dark, in November. Almost nothing else in the app gives you that combination of physical activation, cold, outdoors, and a decision you had to make.

If you want a cheap way to raise tomorrow's score, the arithmetic is simple: a 30-minute sea swim is worth +7 points. The same time on social media, past the free allowance, costs -6.

If cold water is not your thing

The points are not the goal. The closest substitutes in the app are:

• Morning daylight (+10 per hour, up to an hour) for the alertness and circadian effect.
• Vigorous exercise (+12 per hour, capped at 90 minutes) for the mood benefit.
• Time in nature (+9 per hour) - the research on nature is a weekly target of about 120 minutes rather than a daily one.

Log the thing you will actually do. A walk you take every day beats a sea swim you dread.