Waterborne Combat Expanded

Some of the iconic locations in Historica Arcanum could host many adventures or quests that can resolve in watery areas, such as the Bosphorus in Istanbul, the River Nile in Cairo and of course the canals in Venice. In this section, some guides and suggestions are presented for underwater combat and many rules surrounding it. The rules presented here are optional.

The rules appearing in the official sources are preserved:

• If a creature does not have a swimming speed (which could be a natural one or it could be granted by magic), its melee weapon attacks are made with Disadvantage unless the weapon is:
• A dagger, javelin, shortsword, spear, or trident.
• Ranged weapons are also affected. The ammunition does not reach beyond the normal range; thus, any attack against a creature outside of range automatically misses. Moreover, attack rolls are made with Disadvantage unless the weapon is:
• A crossbow, a net, or a thrown weapon (javelin, spear, trident, or dart)
• Creatures and objects that are fully in water have resistance to fire damage.

The rules on weapons and other items are expanded in this section.

Swimming Speed

Since Venice is a water-based setting due to its unique topography, most creatures in the Bestiary have a swimming speed to enhance their efficiency in on-water or underwater combat scenarios. The swimming speed enables creatures to effectively fight combat in and on water as well as contribute to interesting combat scenarios. Below, there are different approaches for player characters to acquire swimming speed.

Optional Rule: Swimming Proficiency

When you gain a skill through your class, feat, feature or background, consult your GM about replacing one of them with Swimming Proficiency. This proficiency enables you to have swimming speed equal to your walking speed.

Optional Rule: Swimming Training

When you spend downtime for the acquisition of a skill or a tool proficiency, you can instead train in underwater combat and how to effectively use your weapons, thus granting you swimming speed equal to your walking speed.

Optional Rule: Obscure Vision

When a creature is fully submerged in water, it is counted as lightly obscured due to water breaking the light.

Optional Rule: Water in Lungs

Many occasions while swimming, especially hazards, combat, strong waves or currents, may trigger a DC 10 Constitution saving throw (or higher depending on the hazard). Swimming in Armor section below provides such an example and running out of breath or some similar situations may be called by the GM to determine the possibility of swallowing water into the lungs. On failed saves, water enters the lungs of the creature and causes some problems for them, especially humanoid creatures.

If the creature is amphibious or can breathe water, water in lungs does not affect them.

While there is water in your lungs, check out the table for possible effects and the Wisdom (Medicine) check made to get rid of it. Unless no check is applied, the effects linger until you finish a short rest, except for Level 4.

Water in Lungs	Medicine Check DC	Effect
1	10	You can't speak.
2	12	You can't regain hit points.
3	14	Your hit point maximum decreases by 1d6 at the start of each of your turns. It is restored after you finish a short or long rest.
4	16	You start to suffocate.*

*Check out the Suffocation section below.

Some events may trigger the saving throw:

• Being drowned by an enemy.
• Running out of air while underwater.
• Having a swimming speed of 0 ft.
• Taking a critical hit underwater.
• Being hit by a powerful wave or wind.
• Any other hazard determined by the GM.
• Any condition that is hazardous enough, such as becoming stunned, paralyzed or incapacitated.

Optional Rule: Breathing Under Water & Suffocation

Holding breath while underwater is also another matter of careful consideration. Regular rules state that creatures can hold their breath underwater for a number of minutes. Unless magic is involved, these optional rules are made to implement a more challenging way for combat.

• Creatures can hold their breath for a number of rounds equal to their Constitution score. For example, a creature with a Constitution score of 14, can hold their breath for 14 rounds.
• Each time a creature is hit with a damage greater than their Constitution score, it loses one round of breath. This also applies at critical hits no matter the damage type or amount.
• After it loses all air, you start to suffocate.
• When it starts to suffocate, it can't regain hit points or can't be stabilized, it drops to 0 hit points and is dying.

Swimming in Armor

One of the most heated debates on tables usually revolves around whether or not characters are able to swim with their armor on, especially there are stories about emperors and kings drowning in their armor while crossing a river (one of the most vivid example would be Emperor Frederick Barbarossa's case during the Third Crusade: He drowned while crossing Saleph River). There are no official rules covering that area and we introduce some options for GMs to decide.

Carrying Capacity

Carrying capacity is usually overlooked in some campaigns to leave out the more crunchy stuff. If your game already takes optional carrying capacity/encumbrance into consideration, use these rules:

• If you are encumbered, you can't use your swimming speed.
• While encumbered, you must make a DC 10 Strength saving throw each time you try to move. On a failed save, you descend 5 ft. and water enters your lungs. If water enters your lungs enough (check out the table above) times in the next minute, you start to suffocate. If you have water breathing through spells or magical effects or some other way, water being in your lungs does not affect you.

Armor Proficiency

If you do not exceed your carrying capacity, the only thing left to consider is armor proficiency.

If you wear armor that you are not proficient with, you are counted as encumbered and the rules above about Carrying Capacity apply to you.

If you are proficient with your armor, different rules apply when you are underwater:

Armor Type	Downside	Upside
Light Armor	Your speed is reduced by 5 ft.	Ranged attacks have Disadvantage against you.
Medium Armor	Your speed is reduced by 10 ft.	Melee attacks have Disadvantage against you.
Heavy Armor	Your speed is reduced by 15 ft.	You take 1d10 less damage from weapon attacks.

Damage Effects & Optional Situations

While fully submerged in water or while swimming in water, damage types may have different effects as well as some of the optional moves and actions introduced in official rules.

Lightning. Creatures take double damage from lightning.

Thunder. Creatures take half damage from thunder.

Cold. If the cold damage exceeds 15, the receiver's movement speed becomes 0 until the end of its next turn. This damage does not trigger the "water in lungs" optional rule.

Strength & Dexterity Checks. Strength and Dexterity checks underwater are made with Disadvantage, unless the creature has a swimming speed.

Gunpowder. Weapons that are considered firearms and rely on gunpowder do not work underwater or if they are exposed to water enough.

Illusions. Characters have Disadvantage on ability checks detecting and discerning illusions that are underwater or somewhat submerged in water due to light's breaking in water.