What you're probably feeling right now
If you've been putting in laps at the lake this summer, or swimming indoors at the rec center through the cooler months, you may have noticed a dull ache settling into the front or top of your shoulder. It's usually worse after freestyle or butterfly sessions, and it often shows up first as stiffness the morning after, not pain during the swim itself.
Some people notice it when reaching for a cabinet or pulling a shirt overhead. Others feel a catch or click partway through the stroke, especially during the recovery phase when the arm comes out of the water. In Rogers, where a lot of people swim seasonally at Beaver Lake in warm months and then move to an indoor pool once the weather turns, this pattern of ramping up and backing off repeatedly is common, and it's exactly the kind of stop-start training that tends to aggravate shoulders.
Why swimmers' shoulders take the hit
Swimming asks the shoulder to do a lot of overhead work, over and over, thousands of times in a single session. The shoulder joint itself is shallow, held together mostly by soft tissue rather than bone, which gives it range of motion but not much natural stability. When the muscles around the shoulder blade get tired or weak relative to the demands being placed on them, the tendons at the front of the shoulder start doing work they weren't built to absorb.
This region's swim season doesn't run evenly through the year. People swim hard in June, July, and August when the lake is warm and outdoor pools are open, then drop off sharply once fall arrives, then maybe pick up again indoors in winter with less frequency. That inconsistency, more than the swimming itself, is often what sets shoulder trouble in motion. Muscles that get strong during a heavy summer stretch lose conditioning fast during a slow month, and then a return to hard swimming finds the shoulder underprepared.
More on this from Shoulder Pain In Swimmers.
What you can check yourself
Start by paying attention to where the pain sits. Pain at the front of the shoulder that comes on gradually and worsens with reaching overhead usually points to the rotator cuff tendons or the biceps tendon nearby. Pain that's sharp, sudden, or came with a specific incident, like a fall or an awkward pull, is a different situation and worth more caution.
Check your range of motion against the other arm. Reach behind your back as if tucking in a shirt, then reach overhead as if hanging something on a high shelf. A noticeable difference between your two arms, either in how far you can reach or how it feels getting there, is useful information. Also notice whether the ache eases with a few days of rest from overhead activity or whether it keeps nagging regardless.
Simple self-care that's reasonable to try on your own includes backing off the volume and intensity of swimming for a week or two, icing after activity if it's sore, and avoiding sleeping on the affected side, which tends to compress the shoulder and make morning stiffness worse.
When it stops being a do-it-yourself problem
If the pain hasn't improved after a couple of weeks of reduced activity, that's a signal the shoulder needs more than rest. Weakness that doesn't go away, a sense that the arm might give out, or pain that wakes you up at night are all reasons to stop guessing and get it looked at properly.
A physical therapist can test the specific muscles and tendons involved, figure out whether the issue is really coming from the shoulder joint itself or from something further up the chain, like tightness in the neck or weakness around the shoulder blade, and build a plan that gets you back in the water without the same problem returning in a month. This is also the point where continuing to swim through pain can turn a minor tendon irritation into something that takes much longer to settle down, so waiting too long rarely pays off.
A note for the seasonal swimmer
Because so much swimming here follows the calendar, tied to lake temperature and pool schedules, it's worth building in a slower ramp-up each time you return to regular laps after a break. Adding distance and intensity gradually, rather than picking up right where you left off the previous season, gives the shoulder time to catch up to the demand. That single habit prevents a lot of the shoulder pain that otherwise shows up every year around the same time.