Lunar Cycles and Tides

The moon and the tides have helped to shape human civilization for millenia. From maritime activities to the simple wonder of the bright celestial body in the night sky, we owe a lot to these natural phenomena. So, I want to write up some simple ideas for using them in a campaign. Let's begin with the moon. Mind you, this only really works if you have one moon, but I imagine you can use the concepts presented here for multiple moons (or ditch them entirely).

Moon Cycles

The moon of Earth is a tidally locked satellite that orbits our planet every 27.8 days. We'll simplify this to just 28 days because I hate decimals. Because it is tidally locked, we always see the same face of the moon most nights. For game terms, we'll have only the important four lunar cycles; new moon, first quarter, full moon, last quarter. Every seven days you'll have a different section of the lunar cycle in the night sky and they will loop back into each other endlessly every 28 days. You'll also notice the in-between sections for crescent and gibbous moons. An easy way to remember gibbous is that it's inverted, like a black crescent moon. When the moon is becoming full, then it is waxing, and when it is becoming new, it is waning.

Source: Wikipedia

Tides

As we now know, the tides are controlled by the moon. Depending on the location of the moon will decide whether we have high or low tide. In game terms, the tides come in and out twice a day. So you'll have two high tides and two low tides. We can have these happen at 6 hour intervals of your choosing. For a bit more realistic tides, you can have the next day's tide times happen about 40 minutes later than the previous day's, but it's not necessary. 

When the tide is coming in, we call that the flow tide. When it reaches it's maximum, that is high tide. You'll see a lot of flooded beaches during this. When the water begins to recede, that is the ebbing tide. When this reaches its lowest point, that is low tide. You will see a lot more of the sand and ocean floor revealed to you. When the tides cease to move, usually at the peak of high and low tide, or when the flow and ebb has stopped, that is slack tide. The different between low and high tide can be one of a couple of feet in depth and several feet in distance from the coast to the ocean.

Tides in the UK on the same day

But that's not all. The phase of the moon can make tides weaker or stronger than normal. The stronger tide is called the spring tide and the weaker tide is called the neap tide. The diagram below shows when this happens. Like the lunar phases, it happens every seven days and alternates between spring tide and neap tide. Generally, it'll lag a little behind the phase of the moon by one or two days. For this exercise, we'll say one day. 

Now What?

So now that we know all this, how do we use this? The tides and their link to the lunar phases have been known as far back as ancient Greece. And they have had a great impact on coastal civilizations for centuries. So some ideas for applying it to game terms.

• Great for nautical games that highly depend on the wind and tides to leave and enter bays.
• Low tide can uncover a secret burial area by the coast.
• High tide hides a secret cavern that leads to treasure. When it's low tide, you can enter it, but traversing it is difficult. High tide, you can easily swim to the different chambers, but it'll be hard to bring stuff out. Not to mention what creatures the tide brings in.
• Low tide reveals a land bridge that leads to a set of ruins, or even an island city that is accessible by bridges.
• High tide can empower water and healing magic, while low tide might stymie it, or instead it empowers earth magic.
• Divination using the tides and what they reveal can be used by scryers and seers.
• Different lunar phases can illuminate the night sky, if only up to dim.
• The different phases can empower different types of magic. Full moon could empower healing and holy magic while the new moon powers summoning and divination magic.
• Lycanthropy is the obvious pointer. You can even say that a ritual during the new moon can help to cure it. Or a ritual under the full moon can make the shift controllable.
• Different deities and protectors of the tides and phases can exist and praying to them at that time can elicit boons.
• Different phases of the moon shining on a dungeon can open different portals that lead to other areas.
• Connections between our world and the spirit world are strongest under a full moon, while the new moon brings in demons and monsters into our world.
• Full moons seem to bring out the worst in people as well as animals. Monsters and creatures become more wild and some people can suffer from lunacy.
• A blue moon (the rare fourth moon in a season) can be the perfect time for a terrible ritual to summon demonic creatures or gather great power. You could even get a wish granted.
• Or the moon could hide a terrible moon presence (spoilers for Bloodborne).

Grand Be during low tide at St. Malo, France

These are what I could come up with. I'd love to see what other ideas people have for using the tides and the lunar phases in their games. Truthfully, before I became a chef, I was into meteorology and I've always had a love of the cycles of nature. So admittedly this is a bit of a self indulgence of that for me, but hopefully this will be useful for those that run great nature campaigns.