​Mastering Tide Cycles for Safe and Seamless Diving

Have you ever pondered the workings of tides and their influence on diving? This curiosity is especially crucial for beach divers, where timing can make entering and exiting the water more challenging, especially during low tide.

For seasoned divers, consulting a tide chart may be routine. However, terms like “Spring Tide”, “Neap Tide”, “Young Tide”, “Slack Tide”, and others might still raise questions.

While Spring Tide and Neap Tide may be familiar, concepts like Young Tide or Long Tide or Slack Tide can be less clear.

In this discussion, we’ll delve into the language associated with tides, making it easier to navigate these natural rhythms.

What Exactly is Tide?

Tides, in essence, signify the rhythmic rise and fall of the ocean levels. (They do also occur in a semi-diurnal (twice daily) pattern on the Great Lakes). Studies indicate that the Great Lakes, Michigan USA, spring tide, the largest tides caused by the combined forces of the sun and moon, is less than five centimeters in height. It may also extend to other lakes on some occasions. This includes high tide, low tide, spring tide, and neap tide. Slack tide is a phenomenon that occurs twice a day during the tidal cycle. It is a period of approximately 30 minutes before High or Low tide when the tide is neither incoming nor outgoing, and the water is relatively still with no or little current, usually the best time for diving in areas of strong current. Collectively, these undulating phenomena are summed up in the term “tide.”

This natural occurrence is primarily set into motion by the Sun’s and Moon’s gravitational pull, particularly on Earth.

The Daily Tide Cycle: Highs and Lows

As the Earth turns around once every day (about 24 hours), the sea levels rise and fall in a regular pattern. When the sea is at its highest point, it’s called high tide, and when it’s at its lowest point, it’s called low tide. 

As the moon changes its position during the day, its closest approach pulls seawater. This gives rise to high tide. On the other hand, when the moon is far away, its pull gets weaker. This lets the Earth’s spinning force have more effect, causing another high tide. 

Midway between these tidal extremities lies the phase known as low tide.

The difference in sea levels between high and low tide can vary from 1 to 2 meters, and sometimes even more. This shift in depth requires vigilant consideration.

The Bay of Fundy in southeastern Canada boasts the world’s most significant tidal range. It can reach an astounding 15 meters!

by Samuel Wantman / Wikimedia Commons / CC BY-SA 3.0 & GFDL

For divers, visualizing the colossal scale of this tidal change should come naturally.

It’s very important to emphasize that the rocks can be slippery when it’s low tide. This makes getting in and out of the water more difficult for divers at the beach. So, exercise caution!

Furthermore, between low tide and high tide, water currents are in full swing. While it tends to be calm during slack tide (around the times of low and high tide), the interim period is when currents are more likely to arise. Keep this in mind!

The Moon’s Cycle and Tide Patterns

In roughly a month, the moon completes a full orbit around the Earth. This orchestrates the ebb and flow of sea levels during this period.
Tides aren’t only governed by the moon’s gravitational force but also by the sun’s. Even though the sun is much bigger and has a stronger pull, it’s farther away. Thus, its effect on tides is thought to be only about half as strong as the moon’s. 

This introduces terms like “Spring Tide” and “Neap Tide,” along with less familiar ones like “Young Tide” and “Long Tide.” These categories define the range between high and low tides known as tide patterns.

• Spring Tide: This phase exhibits the most pronounced difference between high and low tides. It usually occurs during the days surrounding the full moon or new moon.
• Neap Tide: This phase is characterized by the smallest difference between high and low tides. It is observed around the first and last quarter moons for a few days.
• Intermediate Tide: This transitional phase sits between Spring Tide and Neap Tide, and vice versa.
• Long Tide: Following Neap Tide, this day is distinguished by a gradual shift between high and low tides.
• Young Tide: This day comes after Long Tide, marking the beginning of a more noticeable shift between high and low tides.
• Slack tide: It is a period of approximately 30 minutes when the tide is neither incoming nor outgoing before High or Low tide.

During the full moon or new moon, when the sun, moon, and Earth line up, like in daily tide patterns, there’s a big change in sea levels. This causes a Spring Tide.

On the other hand, during half-moon phases, the fluctuation in sea levels is minimal, leading to a Neap Tide.

As a fundamental rule, each type of tide follows a consistent pattern occurring approximately every 15 days:

Young Tide
Intermediate Tide x2 times
Spring Tide x4 times
Intermediate Tide x4 times
Neap Tide x3 times
Long Tide
Young Tide
Intermediate Tide x2 times
Slack tide

However, since the moon takes about 29.5 days to complete one orbit around the Earth, there’s a half-day discrepancy that needs accounting for. To rectify this, the occurrence of Spring Tide decreases by one day every four tidal cycles.

In general, it’s believed that during Spring Tides, when tidal movements are particularly active, fish tend to be more energetic. Fishermen targeting squid, which prey on fish, tend to be more focused during Young Tides.

Spring Tides, with their noticeable differences between high and low tides, often lead to more robust currents. Neap Tides and Long Tides usually involve gentler currents.

The Annual Cycle

As the Earth completes its orbit around the Sun in a year, this celestial dance affects tide levels.

This influence is particularly evident in the timing of high and low tides. During a Spring Tide, for example, the contrast between high and low tides tends to be more pronounced during summer days. In winter, it tends to take center stage during the nighttime.

Navigating Tide Charts

Assessing high and low tides, along with the day’s tidal pattern (be it Spring or Neap Tide), can enhance your diving experience. It will ensure both safety and enjoyment! But how can you check the tide details for the day?

As we’ve discussed, tidal levels are influenced by the gravitational pull of both the moon and the sun.

Since the Earth, moon, and sun move in expected ways, we can predict their impact, including on tide levels. 

While real observed tide levels might vary a bit because of things like air ambient pressure, the times of high and low tides won’t change a lot. 

You can find these predictions in many places. Meteorological Agencies give forecasts for tides and sea levels up to about a year ahead.

This means you can visit any agency’s website and retrieve the tide information for the day and location where you plan to dive. Since the exchange of tides effect surfers as well, you can find tide charts at your local Surfer’s shop.

Keep in mind that tide information is specific to locations. This is because the features and topography of a specific area also influence tidal level predictions. So, even if you’re eager to know the tide forecast for your exact location, there currently isn’t a method to do so.

Even if you shift in location, the times of high and low tides won’t deviate significantly. Thus, we recommend you find the nearest location with tide predictions from where you plan to dive.

Note: Dive locations with many Islands such as in the Pacific Northwest including Canada’s West coast and Indonesia will have stronger currents due to the tide exchange navigating around all the islands. For this reason, it is important to plan your dives there during Slack tide.