Designed by Claire Martin

This puzzle forces characters to think critically and work together to outmaneuver the lurking threat below the surface. They must calculate distance, leverage the magical boat, and plan strategic lures to cross the water safely without succumbing to the relentless menace. Will they sink or swim?

By the way, if you're looking for even more puzzles and other GM resources, check out Lair Magazine #46, Tyranny & Trepidation. It includes two short adventures for levels 3 and 8, five horror-inspired locations, five puzzles, two full-length adventures designed for levels 2 and 17, and an article detailing how to create your own horror adventures! Or check out the bundles and yearly subs to learn how you can get more resources and save big.

Something in the Water - 5e

Difficulty: hard

Something in the water catches up with swimmers and keeps them from getting all the way across. Characters need to calculate distance and plan strategic lures to reach the other side of the water in one piece.

The ground falls from beneath your feet, and you plummet into ice-cold water. Several shadows linger beneath the surface, but one springs to life and begins swimming fast—way too fast—towards you. The remnants of the splash bump you up against a slimy rock, which you scrape and clamber onto just before the shadow reaches you. Two more large rocks emerge from the watery depths, like steppingstones for a giant across a vast pond. A small, rickety boat rests docked at the edge of the first rock. The water sits still, glassy, and dark. The shadow hovers patiently and menacingly below the surface.

Puzzle Features

Characters find themselves on a flat rock that spans 5 feet across. The middle rock is identical in length, while the last is double the size. The span of water between the first and second rock is 115 feet, and the span between the second and third rock is 70 feet. There are roughly 5 feet of water on either end of the first and last rock.

The boat is flimsy and has a hole in it. It can transport one medium or large creature at a time (or two small creatures). It can make two trips between the first and second rock before sinking. After it ferries one creature to the middle rock, it magically returns on its own to the first rock. It sinks after ferrying the second creature across.

Characters take their turn first. Magical abilities do not work in this area. They can swim up to half their movement speed and may use their dash action to double the distance. Once a creature exits the water, they are stunned for one round from the frigid cold.

The thing in the water moves after all the characters’ turns and swims 40 feet toward the creature closest to it in the water. If two creatures are equidistant from it, it pursues one of the two at random. At the beginning of the puzzle, it floats right below the first rock. If it reaches any of the creatures, it deals a dangerous amount of damage (alternatively, if you’re interested in grimmer consequences, it drowns them).

Solution

The characters will need to follow a couple of strategies to get to the other side without harm.

There are five locations where the thing in the water could move to at the end of the round: beneath the first rock, a third of the way through the first stretch of water, two-thirds of the way through the first stretch, beneath the second rock, half-way through the second stretch, and beneath the third rock.

Assuming none of the characters can exceed the speed of the thing in the water, the first move must be to use the boat to ferry a character to the middle rock. The second move must be for that character to swim for the third rock.

Next, a character must be able to swim 25 feet or more per round to make it across the first stretch while a person on the third rock lures the thing in the water away from them. Any creature slower than that must take a boat ride across.

Finally, the characters must reserve the second boat ride so the last person can leave the first rock. Before they leave, they must also lure the thing in the water to the first rock so they can swim the second stretch without being overcome.

Hint Checks

Wisdom (Survival) DC 5. The character can’t identify what the thing in the water is, but they are certain that its purpose is malevolent. Their best bet is to avoid it altogether.

Intelligence (Nature) DC 10. The thing in the water can move 40 feet every round, and it will always chase after the creature closest to it in the water.

Intelligence (Arcana) DC 15. There are no oars or sails on the boat, but it will magically carry a passenger to the second rock before returning on its own. However, the boat has a hole, so it’ll only survive two trips.

Customizing the Puzzle

This puzzle works well on a river, lake, pond, or in a flooded room.

Lowering the Difficulty. To simplify this puzzle, disregard the stunned condition when a character exits the water. This allows them more breathing room to lure the creature to one side or the other.

Something in the Water

Difficulty: hard

Something in the water catches up with swimmers and keeps them from getting all the way across. Characters need to calculate distance and plan strategic lures to reach the other side of the water in one piece.

The ground falls from beneath your feet, and you plummet into ice-cold water. Several shadows linger beneath the surface, but one springs to life and begins swimming fast—way too fast—towards you. The remnants of the splash bump you up against a slimy rock, which you scrape and clamber onto just before the shadow reaches you. Two more large rocks emerge from the watery depths, like steppingstones for a giant across a vast pond. A small, rickety boat rests docked at the edge of the first rock. The water sits still, glassy, and dark. The shadow hovers patiently and menacingly below the surface.

Puzzle Features

Characters find themselves on a flat rock that spans 5 feet across. The middle rock is identical in length, while the last is double the size. The span of water between the first and second rock is 115 feet, and the span between the second and third rock is 70 feet. There are roughly 5 feet of water on either end of the first and last rock.

The boat is flimsy and has a hole in it. It can transport one medium or large creature at a time (or two small creatures). It can make two trips between the first and second rock before sinking. After it ferries one creature to the middle rock, it magically returns on its own to the first rock. It sinks after ferrying the second creature across.

Characters take their turn first. Magical abilities do not work in this area. They can swim up to half their movement speed and may use their dash action to double the distance. Once a creature exits the water, they are stunned 3 from the frigid cold.

The thing in the water moves after all the characters’ turns and swims 40 feet toward the creature closest to it in the water. If two creatures are equidistant from it, it pursues one of the two at random. At the beginning of the puzzle, it floats right below the first rock. If it reaches any of the creatures, it deals a dangerous amount of damage (alternatively, if you’re interested in grimmer consequences, it drowns them).

Solution

The characters will need to follow a couple of strategies to get to the other side without harm.

There are five locations where the thing in the water could move to at the end of the round: beneath the first rock, a third of the way through the first stretch of water, two-thirds of the way through the first stretch, beneath the second rock, half-way through the second stretch, and beneath the third rock.

Assuming none of the characters can exceed the speed of the thing in the water, the first move must be to use the boat to ferry a character to the middle rock. The second move must be for that character to swim for the third rock.

Next, a character must be able to swim 25 feet or more per round to make it across the first stretch while a person on the third rock lures the thing in the water away from them. Any creature slower than that must take a boat ride across.

Finally, the characters must reserve the second boat ride so the last person can leave the first rock. Before they leave, they must also lure the thing in the water to the first rock so they can swim the second stretch without being overcome.

Hint Checks

Survival DC 15. The character can’t identify what the thing in the water is, but they are certain that its purpose is malevolent. Their best bet is to avoid it altogether.

Nature DC 20. The thing in the water can move 40 feet every round, and it will always chase after the creature closest to it in the water.

Arcana DC 25. There are no oars or sails on the boat, but it will magically carry a passenger to the second rock before returning on its own. However, the boat has a hole, so it’ll only survive two trips.

Customizing the Puzzle

This puzzle works well on a river, lake, pond, or in a flooded room.

Lowering the Difficulty. To simplify this puzzle, disregard the stunned condition when a character exits the water. This allows them more breathing room to lure the creature to one side or the other.

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