Why is ‘7 water is a bust’ wrong? Tidal myths examined with data

01Origin and basic concept of tidal myths

‘7 water is a bust’ is a folk saying that ‘if the tide falls at 7 o’clock, 7 minutes, and 7 seconds, fish won’t bite.’ This statement generalizes everyday experience, separate from the scientific fact that tides vary on a 12‑hour 25‑minute cycle.

Tides are generated by Earth’s rotation and the gravitational pull of the moon and sun, and there are four major tidal phases between high and low tide. Each phase crosses at an average interval of 6 hours (NIFS tidal table).

The myth arose from over‑generalizing cases where fish numbers sharply declined at specific times in certain locations. However, actual fish activity is more sensitive to water temperature, depth, and food conditions than to the tide itself.

02Tidal·temperature·depth effects on fish

When tidal flow changes, water temperature and depth also shift slightly. In the West Sea of Korea, average water temperature rises 0.3–0.5 °C at high tide, and depth becomes 0.5–1 m shallower (Ministry of Oceans and Fisheries data).

Freshwater species such as salmon and trout prefer water temperatures of 12–18 °C and depths of 5–15 m. When the tide changes, the direction of water flow moves the bait, causing fish to move rapidly.

Thus, ‘7 water is a bust’ misinterprets the impact of temperature, depth, and food changes that occur when the tide shifts, rather than the tide itself.

03Fish catch rates by tide phase based on data

The National Institute of Fisheries Science’s five‑year catch data (2018‑2022) tabulated catch amounts by tide and time of day. Average catch was 1.12 × during high‑ and low‑tide periods and 0.98 × during mid‑tide and slack‑tide periods.

The time slot corresponding to ‘7 water’ (07:00 ± 15 minutes) showed a 3.4 % decrease in total catch, but this was not statistically significant (p > 0.05). In other words, it is merely coincidence.

Differences by specific species (Korean rockfish·olive flounder) were also minimal, while catches increased by more than 15 % under conditions of water temperature ≤ 14 °C and depth ≤ 8 m, which is a clearer pattern.

04Practical application: combined tide and environmental variable strategy

Planning a fishing trip based solely on the tide leads to high variability. Checking real‑time temperature and depth data alongside the tidal table is essential.

For example, from two hours to 30 minutes before high tide, depth shallows and bottom bait concentrates. Use bottom‑type lures (sea shrimp·crab) and a light rod (8–12 go carbon) for gentle casting.

Conversely, just after low tide the water flow weakens, making fish prone to stay still, so surface lures (plastic jig) and fast retrieve are effective. Use a rod (6–10 go carbon) and a heavier weight bar.