Deep sea exploration is one of the trickiest things to represent in a TTRPG. Not only are the logistics and challenges of plumbing the depths complex and tedious, not a lot of compelling fantasy or sci-fi adventures are framed with this in mind. There is one recent D&D adventure that has underwater sections, but even there it is not a central focus. But there is a certain mystique that comes with exploring such unknown stretches of the map. This is where the DMs Guild book, Beneath The Waves, attempts to unearth its own fantasy.
What New Rules Are In Beneath The Waves?
Beneath The Waves makes a solid first impression, providing in-depth rules not just about underwater traversal but how it affects creatures, objects, and certain spells. The gazette includes rules on buoyancy, additional rules on breath and suffocation, and there are even additional rules for different levels of water depth and natural phenomena such as brine lakes or the Midnight Zone. There are even a few light environmental rules such as how certain elemental spells work underwater, changes to player senses like vision and hearing, as well as how players deal with different levels of water pressure.
Overall, these rules work really well. The most lethal of these effects include the affects of rapid depressurization, which can lead automatically to five levels of exhaustion. Furthermore, those levels can only be recovered while inside a new magic item provided in the book: a decompression chamber.
The only new rule that can feel counterintuitive is how underwater movement works. Basically, in addition to having a field of movement for horizontal movement, you also have a separate pool for ascending or descending. Part of this is to ensure that players take their time going deeper to avoid the aforementioned environmental effects, but it can be hard to keep track of with a map and miniatures. If you're really good at abstract thinking or just keep track of the rate of each player's descent, this won't be a problem, but it can take some getting used to.
What New Player Options Are In Beneath The Waves?
Surprisingly, Beneath The Waves includes some well thought out player options as well. There are three player races. The most conventional are the Merfolk, which can easily be slipped into any deep sea adventure. The Campana are jellyfish people that act as an underwater answer to plasmoids. Finally, there are the Caraspians, crablike humanoids that gain different benefits from things they have eaten.
The material also includes two new subclasses. The Ocean Domain Cleric adds some welcome wrinkles to the archetype including a Channel Divinity that brings a tidal wave to the battlefield. But my personal favorite has to be the Hydromancy Wizard. D&D 5e has leaned too hard on fire when it comes to elemental damage and this wizard school tries to bring some versatility back. This includes adding some new functions to the shape water cantrip, pushing targets around the battlefield with high pressure water jets, and an ability that adds extra battlefield mobility and a chilling twist to spells.
What New Creatures and Items Are In Beneath The Waves?
If you are looking for more GM materials, Beneath The Waves does provide more than some deep sea exploration rules. The book is packed with magical items. Some are connected to the new rules such as the Aquabubble and the Dive Belt. Others are fun twists on seafaring tools like the Reefcaller Trident, which can call forth underwater steeds and be returned after being thrown, or the Sparrow's Compass which leads to the user's greatest desire.
There's also an effort to include some diverse underwater life in the book. This includes adorable entries like the Kelp Shepherd and the Leaf Sheep. But there are a few unsettling monster entries to be found as well. If you thought mimics were bad above ground, the Deadwood Mimic takes that terror to the darkest depths.
Finally, there is a prewritten adventure in Beneath The Waves that helps showcase all of this new content. The Blue, The Fresh, and The Ever Free takes players from levels 1-5 and tells a story of corrupt officials, mad kuo-toa doctors, and saving a reef of people from oppression. There's a lot of charm in the adventure, showcasing different characters and scenarios while getting players' minds racing about other aquatic adventures. The book even contains complex motivations and goals for all major NPCs as well as content warnings for certain story turns. Probably my favorite part of the book is an extensive character background process. This helps your group flesh out their history with the areas in the adventure and help give them some more motivation aside from “stop the bad guy.”
My only major critique of the adventure is that it pulls statblocks and spells from multiple D&D books. The opening chapter even includes a list of books you will need on hand for reference. Some of these include player supplements like Xanathar's Guide to Everything or Tasha's Cauldron of Everything, but they also include more esoteric material from Storm King's Thunder, Tomb of Annihilation, and Eberron: Rising From The Last War. Substitutions and homebrewing are always an option, but if you plan on running the adventure as written, just know there are some walls to get through.
Should I Buy Beneath The Waves?
If you've ever wanted to take a Dungeons & Dragons adventure under the sea but found the standard rules underwhelming, I highly recommend Beneath The Waves. While the new mechanics for water exploration will take some getting used to, the new creatures, items, and subclasses are a treat. Plus, it has a great starting adventure that helps players engage the events of the story.
The copy of Beneath The Waves used in this review was provided by the publisher.