I need three full days to recover from a surfing lesson despite training regularly — is that normal?

Three days is at the far end but it is not alarming for a month in, and the explanation is that gym strength transfers to surfing much less than you would expect.

What you are doing in the water:

• Paddling, which is prolonged, continuous shoulder and upper back endurance work. Weight training is typically sets and rests; paddling is twenty minutes of unbroken effort at a moderate load. Completely different demand, and it is the main reason beginners are wrecked.
• Holding an arched position on the board for long periods, which loads the lower back and neck isometrically in a way essentially nothing else does.
• Repeated pop-ups, which are explosive and eccentric and land in unfamiliar positions.
• Being cold and being knocked about, both of which cost more than people account for.

Beginners also spend far more time paddling and far less time riding than they expect, so the session is mostly the endurance component.

The other factor is that unfamiliar movement produces disproportionate soreness the first several times, and then stops.

This is well described: the first exposures to a new pattern, particularly one with a lot of lengthening under load, produce far more muscle soreness than the same work does once you have adapted. The effect is large and it fades quickly with repeated exposure.

So the expected trajectory is that this improves substantially over the next month or two, and it will improve faster if you surf more often rather than harder. Two shorter sessions a week will build tolerance more quickly than one long one, because the adaptation is driven by exposure.

If it is not improving at all after two or three months of regular surfing, that is worth looking into — but at one month, this is the normal course.

One practical note: rough water multiplies everything, exactly as you observed.

On a messy day a beginner spends far more time paddling against water, gets pushed back, duck-dives or gets rolled repeatedly, and rarely gets a clean ride. The session can be double the work for a fraction of the reward.

While you are building tolerance, choosing calmer days is not avoiding the challenge — it is choosing the sessions where you learn most per unit of fatigue.

For the gap in your gym training, the specific things that transfer:

• Horizontal pulling endurance. Higher repetition rows and pull-downs, sets in the fifteen to twenty-five range, which is unusual for a strength programme but matches what paddling asks for.
• Anything for the back of the shoulder and the mid-back. These are the areas that limit paddling and the ones a general programme under-trains.
• Extension endurance — holding an arched position, which is exactly the surf posture.
• General aerobic work. Paddling is a cardiovascular effort as much as a muscular one, and this is usually the missing piece for people who only lift.

Add those and the first month of any paddling sport gets noticeably easier.