There is a particular kind of stubbornness that open water swimmers know well. You drove to the beach. You squeezed into your wetsuit. The water is right there. Surely it will be fine.
Sometimes it will be. And sometimes that stubbornness puts you in real danger.
The best open water swimmers are not the ones who swim through anything. They are the ones who know when to call it off. Here are five signs that today is not your day, and why making that call is a sign of experience, not weakness.
1. There Is a Red Flag or Active Advisory
This one should be non-negotiable, but every year swimmers ignore posted warnings and pay for it. Red flags, beach closures, and hazard advisories exist because trained professionals have assessed the conditions and determined they are dangerous.
Common advisories include:
- Red or double red flags indicating dangerous surf or currents
- Water quality warnings from bacterial contamination, algae blooms, or sewage overflows
- Marine life advisories for jellyfish swarms or shark sightings
- Small craft advisories that also affect swimmers in open water
It does not matter how strong a swimmer you are. An advisory is not a suggestion. If the beach is closed or flagged, respect the call.
SwimPass pulls in real-time advisory data for your saved swim spots, so you can check before you even leave the house. A two-second glance at the app can save you a wasted trip, or something far worse.
2. There Is Thunderstorm Activity Within 30 Minutes
Lightning and water are a lethal combination, and this is one of the most underestimated risks in outdoor swimming. If you can hear thunder, the storm is close enough to be a threat. The general rule is simple: if thunder roars, get out of the water and stay out for at least 30 minutes after the last rumble.
What makes this tricky is that storms can develop fast, especially in summer. A clear sky at 7 AM can turn electric by 8:30. And if you are out in the middle of a lake or bay, you are the tallest object on a flat plane of water. That is not where you want to be.
Before heading out, check the forecast for your swim window. SwimPass's SwimScore factors in thunderstorm probability and will drop sharply when electrical activity is in the area. If the score is suppressed and you are not sure why, storm risk is often the reason.
3. You Are Feeling Unwell, Exhausted, or Off
This is the sign that swimmers are most likely to ignore, because it feels like an excuse rather than a reason. But your body's condition is just as important as the water's condition.
Swimming when you should not includes days when you are:
- Fighting off illness -- even a mild cold affects your breathing, energy, and ability to respond to unexpected situations
- Sleep-deprived or deeply fatigued -- reaction time and judgment suffer, both of which matter in open water
- Hungover or dehydrated -- your cardiovascular system is already stressed
- Recovering from injury -- especially anything affecting your shoulders, core, or breathing
Open water swimming is not a pool. There are no lane ropes, no walls to grab, and no lifeguard watching your lane. If something goes wrong, you need reserves of energy and clarity to get yourself to safety -- our open water swimming safety guide covers emergency procedures and self-rescue techniques. If those reserves are already depleted before you get in, the margin of error shrinks dangerously.
Give yourself permission to rest. The water will be there tomorrow.
4. Water Visibility Is Very Poor
Murky water is not just unpleasant. It is a genuine safety concern for several reasons.
When you cannot see below the surface, you cannot spot submerged hazards like rocks, debris, or drop-offs. You lose your sense of depth and orientation. In coastal areas, poor visibility can also indicate strong currents churning up sediment, which is its own warning sign.
Turbid water also makes it harder for anyone on shore to spot you if you are in trouble. And in areas with marine life, low visibility increases the chance of surprising an animal that would otherwise have moved away.
Some degree of reduced visibility is normal in open water, and experienced swimmers adapt to it. But when you truly cannot see your hand in front of your face, especially in an unfamiliar spot, the smart move is to wait for better conditions.
SwimPass displays water visibility estimates based on recent conditions, wave action, and weather patterns. If you are planning a swim in a new location, checking this data point ahead of time can help you set expectations.
5. The Conditions Are Beyond Your Skill Level
This is the hardest sign to recognize, because it requires honest self-assessment. But it might be the most important one on this list.
Open water conditions exist on a spectrum, and what is manageable for an experienced ocean swimmer can be genuinely dangerous for someone newer to the sport. Learning to understand water conditions is one of the most important skills you can build. Factors that escalate difficulty include:
- Wind speed and chop -- even moderate wind creates waves that affect breathing and sighting
- Current strength -- river currents and ocean drift can overpower a swimmer who underestimates them
- Swell size and period -- large swells change the game entirely for coastal swimmers
- Water temperature -- cold water saps energy faster than most people realize
- Distance from shore -- the further out you are, the higher the stakes
There is no shame in looking at the conditions and deciding they are beyond what you are comfortable with today. Experienced swimmers do this regularly. It is how they became experienced swimmers.
SwimPass's SwimScore is designed to help with exactly this kind of decision. It adjusts recommendations based on your selected ability level, so a set of conditions that scores well for an advanced swimmer might flag as cautious for a beginner. It is not a replacement for your own judgment, but it is a useful gut-check when you are standing on the shore trying to decide.
The Bigger Picture
Every one of these signs comes back to the same principle: the goal is to swim again tomorrow. One skipped session is meaningless in the long run. One bad decision in open water can change everything.
Build the habit of doing a quick conditions check before every swim. Look at the flags, check the forecast, listen to your body, assess the water, and be honest about whether the conditions match your abilities. Over time, this becomes second nature, a quick mental checklist that takes less than a minute.
And on the days you decide to skip? You have not lost anything. You have made the most experienced decision possible.
Swim smart. Swim often. Swim tomorrow.