Tactics 101: Aquatic Combat

I love 4th Edition for the simplicity it has to offer.  The rules are easy to follow and learn, play time is simpler (you do not have to reference all the books with the online compendium handy), and roleplaying is encouraged and necessary to differentiate yourself from other characters.

The following post will cover the basics of an aquatic setting and give some tactics to use against some of these monsters.  Aquatic combat has so much untapped potential in the game; there is so little written about it.

Sure, adventurers can teleport to strange exotic places in a heartbeat, travel to different planes and even travel into the cosmos, without anything hampering their way.  Put them in a little bit of H20 and all hell breaks loose.
Most aquatic combat is assumed to take place on a shore, ship, or raft (like the Crystal Cave Session 7), where the party members are at little or no risk of drowning.  The information I would like to touch on today is related to the deep sea where creatures of impressive size throw you into the water, where adventurers have to fight there way out of encounters where the monsters have the home advantage.

Here are the rules that pertain to combat in the aquatic setting.

1. Adventurers using powers with the fire keyword take a -2 penalty to their rolls.
2. Adventurers using weapons from the spear or crossbow group of weapons take no penalties.  All other weapon groups take a -2 penalty to attacks.
3. Adventurers who are in the water must make an athletics check to stay afloat or swim(above or under the water).  The DC are the following; 10 for calm waters, 15 for rough waters, and 20 for stormy waters. Adventurers with no swim speed move only at half speed on a successful check.
4. Failure of these checks by 4 or less results in the character staying afloat but no being able to go anywhere, failure by 5 or more the character sinks 1 square and begins to hold its breath(see below)
5. While underwater the adventurers can hold their breaths up to 3 minutes (this is not a problem for most encounters, but if your adventure is set deep underwater, then the following rules apply)
6. If the adventurer can no longer hold their breath, they must begin rolling endurance checks. The first check is DC 20. Failure means you lose 1 healing surge, and if you have no remaining surges, you lose HP equal to half your level per round. Each round after the first, increase the DC by 5.  Same penalties apply.
7. If a character takes damage from an attack while holding their breath they must roll an endurance check DC 20 at the end of their turn.

Here are some general rules that pertain to swimming:

1. A successful athletics check allows the adventurer to swim half their speed.
2. An endurance check must be made for every hour a character is swimming.  This check is DC 10 calm, DC 15 rough, and DC 20 stormy.  Failure of this check and the player cannot swim any longer without taking an extended rest.  
3. If the check is successful the character can continue to make athletics check to continue swimming.  These endurance checks must be made with a + 2 to the DC every hour the character is swimming.

Helpful Powers, Items and Rituals

Deft Diver, Elemental Transmogrification, Primal Cascade are all example of powers that could be useful to the party for combats underwater.  Unfortunately, most characters would be hesitant to take any of these powers because of the frequency of aquatic settings.

Consumables and Items would probably be the better way to go.  You can always keep them on you and when in need...  Here are a few consumables of interest: Elixir of Water Breathing, Shoes of Water Walking, Pearl Sea Horse.  These items are relatively inexpensive, especially at higher levels.  

The rituals that are useful are the following: Water Breathing, Waterborn, are probably two of the most important rituals to help you along your way.

First Order of Combat

1. Everyone should do knowledge checks before the encounter begins to see what the creature is, to assess any weaknesses or vulnerabilities it has and what some of its power may do.
2. Designate the defender to protect the Controller. This way, staying adjacent to the Contoller offers this PC cover (+2 bonus to all defenses) in case the aquatic creature decides to target the squishiest PC fist. Defenders typically have higher AC and hit points than most of the characters on the battlefield.  The Defender should ready an action to attack (and mark) any enemy that comes into range of his weapon.

Tactical Movement

I would probably attempt to flank the creature and box it in, in three dimensions to prevent it from having the advantage of moving around (swim speed advantage).  The other advantage to the boxing in effect is that the characters are spread out, so any blast effect only targets one or two PCs at a time.

Make sure that if you have a weapon from the spear or crossbow category, that you take it out so you are not penalized -2 to attacks, unless you have a power that functions underwater (see above). 

Unless you have a swim speed, chances are you will have to move at half your speed.  A good tactic would be to provoke an opportunity attack to get into good positioning.  Sometimes you have to take one on the chin for the team to come out ahead.

Do you have any more tactics than the ones I bring to the table?  Have you ever fought combat underwater?  How did it go?