Illustration by Geoffrey Ernault

Underwater adventuring is one of those things that older editions of Dungeons and Dragons seemed to like more than their players did. Lots of monster books included a selection of monsters that could only be encountered under the sea, but every bit of commentary I read on those was always about how no one ever bothered to include submarine delves in their campaigns. If a sea monster couldn’t go up to the surface to attack a ship or climb on its deck, it was usually ignored by GMs.

The Dungeon Fantasy lines learned this lesson well, and don’t spend a lot of ink on support for underwater adventures. This was a big problem for me when I was GMing Hell’s Rebels to a group of friends. This particular adventure path follows the old tradition of making PCs spend a chunk of levels 5-8 underwater. When I got to that part in my GURPS conversion, I had no idea what to do and got a bit stressed out trying to figure this out on the spot.

Frantically researching rules in real time is no fun at all even when I am the only player, so for the benefit of my solo Hell’s Rebels game and any future run-throughs with actual players, I’m going to collect everything I know about fighting underwater in GURPS right here in this post.

I admit I don’t have all the officially published primary sources that discuss underwater adventuring. The ones I’m using are DF: Exploits and the simplified rules that can be found in Dungeon Fantastic, which do reference the sources I don’t have.

Underwater Fighting For Land-Lubbers

If you’re not an aquatic creature, you use these rules when fighting underwater.

  • Your Move is limited to your Swimming move: Basic Speed/5, minimum 1.

  • All of your skills are capped at the level of your DX-based Swimming.

  • Thrusting and unarmed strikes receive no penalties.

  • Some grappling techniques won’t work. Others work as normal. GM adjudicates.

  • Swinging attacks with Reach 1+ weapons are impossible. This does cover pretty much every weapon listed in DF: Adventurers, as even small knives have a Reach of “C, 1” when swung.

  • Shield bashes are -2 x DB to hit and do half damage. Don’t bother trying.

  • Blocks are impossible but you still get your shield’s DB.

  • Parries with Reach 1+ weapons are impossible. Parries with close-combat-only weapons like daggers, and unarmed parries, are allowed and suffer no penalties.

  • Dodge is possible and not penalized, but you can’t Retreat.

  • No thrown ranged attacks, even from Missile spells. Special underwater ranged weapons exist and use specific stats.

  • Ranged attacks into our out of water have -4 to hit, 1/10 range, and do half damage.

  • All through this, you’ll be holding your breath under Heavy Exertion (DF: Exploits p. 21)!

Underwater Fighting for Fish and Fish-People

Water adaptation in GURPS has two main components. One is the ability to breathe underwater. The other is the ability to move freely while submerged.

In monsters, the first is handled by traits such as Gills, some variety of Doesn’t Breathe, or the ability to hold their breath for a really long time even in combat. A combatant with one of these traits doesn’t need to worry about the standard Breath Holding rules.

The second is handled by the Amphibious or Aquatic traits. If you have one of these traits, you get a lot of advantages over land-lubbers.

  • Your get to use your full Move and skills, not limited by your Swimming.

  • You are exempt from most skill penalties from being underwater and from many Swimming tests.

  • You can Retreat!

  • Your other attacks and defenses are limited as for land-lubbers. This is important for weapon users, not so much for aquatic beasts.

From Delver to Diver

If you’re a typical delver belonging to one of DFRPG’s standard ancestries, then you fall squarely in the “land-lubber” category, and you have to solve a couple of problems before you can dive in.

Breathing

If you don’t want your underwater life expectancy to be measured in seconds, you need to find a way to breathe in there. In most typical DF settings, that means magic.

Spells

The DFRPG boxed set includes two main drowning-prevention measures: the Breathe Water and Hold Breath spells. They have different prerequisite chains but work the same, letting you ignore that part of the rules for as long as they last. Both have a base duration of 1 minute and an energy cost of 4 to cast and 2 to maintain, reduced by skill as normal. Hold Breath is a little better because it also let you survive in non-watery environments.

Their main disadvantage is that their duration is relatively short. Unless the PC casting these spells has a skill of 20 or more with them, the affected character is only going to be able to remain underwater for a few minutes at a time. That’s nowhere near enough for a full delve, and it’s an even shorter time if you need to maintain this spell for multiple PCs. If the caster does have skill 20 then things get a lot easier, but that costs a lot of points.

Items

If we expand our scope a little to look at DF supplements, then we see that Dungeon Fantasy Magic Items 1 has an alchemical Water-Breathing Amulet. You can breathe underwater as long as you wear it… but it costs an amazing $23.400. Outfitting a party of 5 with that is a very expensive proposition, unless you find them as treasure.

A reusable casting item like a wand or ring with the Breathe Water spell would cost at least $8200. This basic version would be powered by the user, so it has the same duration limits as the spell. Doubling the price would halve the energy cost, which is better but not perfect.

However, if we expand our scope even further and break out of the DFRPG bubble, we can go to GURPS Magic and find an alchemical water-breathing elixir that costs $600 in a setting with common magic and gives you the ability to breathe water for 1d hours! Even a minimal roll gives you a nice amount of time to explore, and per that book’s rules you’ll know the duration is about to expire 5 minutes in advance, which is better than nothing.

That elixir is clearly the best approach for campaigns where underwater delves are a sometimes thing. They’re a little less convenient than the amulet, but the price can’t be beat. I’m definitely including this in my campaign.

Moving

Unless your delvers are willing to spend the time and points to become better-than-Olympic swimmers, solving their underwater movement issues also means resorting to magic.

Spells

DF: Spells gives us two options here: Swim and Ethereal Body. The first makes the subject effectively Amphibious, the second makes them intangible and thus able to ignore all that water. GURPS Magic additionally gives us Walk Through Water, which makes the user intangible only to water and ice. This means you don’t enjoy 3D movement while underwater… but your maneuvers in combat are unrestricted! I think I can kinda see why this one didn’t make the cut to the DFRPG.

As with water-breathing, our biggest limitation here are spell maintenance costs, which limit our unimpeded movement to a few minutes at most. These are also harder to completely eliminate, since Ethereal Body costs 4 energy per minute to maintain and the others cost 3. Still, a caster could conceivably save these for when a fight is about to start, and only cast it on the group’s physical fighters.

Magic Items

I couldn’t find an always-on item with a Swim enchantment in the books I own. A basic casting item for Swim will cost at least $20500, almost as expensive as the always-on water breathing amulet. Lowering its casting/maintenance cost from 6/3 to 3/2 doubles the price, lowering it to 2/1 quadruples it.

We might built this as a charged item instead, with each charge giving you 2 minutes of Swim time and costing 9 energy. A non-rechargeable item would cost $1350 per charge, a rechargeable one $2700 (plus $180 per charge to reload).

If Walk Through Water is allowed in the campaign, an item with the same duration per charge would be a tad cheaper: $910/$1820/$140.

In any of these cases, the item is best used sparingly, in the same manner as the spell. You activate it when it’s time for a big fight or a crucial skill test, and rely on your Swimming lessons the rest of the time.

Optimal Strategies

Given all of the above, I think we can pretty easily arrive at an “optimal” strategy for underwater expeditions.

If your group is about to embark in a campaign centered around underwater delving, your PC party should include a caster who can use Breathe Water at Skill-20, and also someone who can use Swim at Skill-15. A druid or wizard could do both, a cleric can use Breathe Water and leave Swim to someone else. This is a hefty investment, but worth it for the amount of use they’ll get out of it. Every PC, caster or not, should also consider investing points into the Swimming skill, because it can help conserve spell energy and is pretty useful in itself. You might want to give them extra points for these purposes depending on your desired power level.

An alternative here is for you to allow players to make PCs from ancestries that have an easy time underwater. Both Sea Elves from GURPS DF 3 and Argonians from this blog have Gills and are Amphibious. Warforged are a bit less nimble but don’t need to breathe at all. Each delver who is a natural-born diver will make the rest of the party’s life that much easier. For those who aren’t, Water-Breathing Amulets make excellent treasure.

If you’re planning a standard campaign that features a one-off underwater dungeon, Water-Breathing Elixirs are the way to go, possibly supplemented by one or two rechargeable Wands of Swimming. The elixirs should definitely be easily available in a nearby town (perhaps it’s a coastal fishing village?). The wands might be for sale as well, or might be found as treasure either before or during the delve. Proper safety procedure is to carry two elixirs per PC, saving the second one for the return trip if the first one wears off.

If you only have isolated underwater encounters, we’re back to learned spells, but they don’t need to have high levels. The submerged environment becomes an additional challenge, but no one is going to spend too long inside it.

Hell’s Rebels in particular fits the second category, so I’ll be using that solution.