Do Weekdays Have Better Diving Visibility Than Weekends? 46,000 Logs Analyzed
2026-03-15
Ever taken a weekday off to dive and felt the water was clearer? From 46,000+ dive logs sorted by day of week, weekdays (Mon–Fri) average 13.5–13.9m while weekends average 13.1m — a 0.6–0.8m gap. Coincidence or science?
13.7m
Weekday avg (Mon–Fri)
13.1m
Weekend avg (Sat–Sun)
Visibility by Day of Week
| Day | Avg Vis | Obs | Type |
|---|---|---|---|
| Sunday | 13.1m | 8,098 | Weekend |
| Monday | 13.7m | 6,484 | Weekday |
| Tuesday | 13.9m | 5,824 | Weekday |
| Wednesday | 13.6m | 6,048 | Weekday |
| Thursday | 13.7m | 6,082 | Weekday |
| Friday | 13.5m | 6,738 | Weekday |
| Saturday | 13.1m | 7,693 | Weekend |
Tuesday (13.9m) is highest, Sat/Sun (13.1m) lowest. The Tuesday-to-weekend gap is 0.8m.
Why Are Weekdays Clearer? Three Hypotheses
Hypothesis 1: Reporting Bias (Most Likely)
Weekends have more guests, and shops operate in all conditions. On weekdays with few guests, shops may close when conditions are poor. This means weekday data may only capture 'good days' — a selection/reporting bias.
Hypothesis 2: Diver-Induced Turbidity
Weekend crowds mean more divers per site, kicking up sediment. This matters especially in bay/sandy-bottom sites. However, this alone probably can't explain a 0.7m difference.
Hypothesis 3: Observer Skill Difference
Weekday divers tend to be experienced, with more accurate visibility estimates. Studies show beginners may underestimate visibility due to anxiety. However, since our data is from shop staff, this effect is limited.
Conclusion: Reporting Bias Is Most Likely
Weekday observation counts are lower (6,000–6,800) than weekends (7,700–8,100), supporting the 'bad weekdays go unrecorded' theory. It's unlikely the ocean actually changes by day of week — data collection bias is the primary cause.
Why Weekday Diving Is Still Recommended
- No crowding → less sediment disturbance, perceived as clearer
- More attentive shop service (smaller groups)
- Easier access to popular dive sites
- Better photos/videos without other divers in frame
About the Data
46,967 observations from 42 nationwide dive sites, grouped by day of week (2006 – Mar 2026). Visibility is mean of daily min/max. Quantifying reporting bias remains a topic for future analysis.
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