Why do Black Dragons need Swim as a skill?

[ksbsnowowl]

One of the bonus class skills that a Black Dragon gets is Swim.  As it has a swim speed, it naturally gets a +8 racial bonus to Swim checks, and can also Take 10 on any swim checks.

However, Black Dragons also have the Water subtype, which states:

Water Subtype:  This subtype usually is used for elementals and outsiders with a connection to the Elemental Plane of Water. Creatures with the water subtype always have swim speeds and can move in water without making Swim checks. A water creature can breathe underwater and usually can breathe air as well.

The bolded portion basically means it is pretty much always treated as succeeding on a swim check to move, right?  If it can move through water without needing to make checks, what is the point of having the skill?

[sirpercival]

For when it has to swim in substances other than water.

[Raineh Daze]

It breathes acid. Acid is not water. Therefore, if it makes an acid lake somehow, it needs swim as a skill to move about in there?

[Nunkuruji]

Doesn't make a lot of sense considering its written into Core

Otherwise, I suppose there's the off chance of using it during Polymorph or if taking Alternate Form (RoE)

[Kethrian]

You'd still need to make checks to "perform a special action or avoid a hazard".

[awaken_D_M_golem]

Well black dragon's don't have modern manufacturing techniques
so keeping the balance between Mud + Black Dragon Acid breath,
requires you to be underwater for a long time.
Works out about like this stuff ---> http://www.awakeningskincare.com/dead-sea-mud-p/fmudface.htm
The thorp Aristocrats have to spend their money somehow.



EDIT --- oh right, a Transmute Mud To Lotion spell.

[SorO_Lost]

How can you do some research, look up the Water Subtype for an Acid based Dragon, and wonder why it has a Racial bonus to Swim?

Specially when

A creature with a swim speed can move through water at its swim speed without making Swim checks. It has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. The creature can always can choose to take 10 on a Swim check, even if distracted or endangered. The creature can use the run action while swimming, provided it swims in a straight line.

Every single creature ever printed has a Racial Bonus and it explains why...

[ksbsnowowl]

How can you do some research, look up the Water Subtype for an Acid based Dragon, and wonder why it has a Racial bonus to Swim?

...

Because I was remembering that part from memory... 

[SorO_Lost]

Because I was remembering that part from memory... 

Alright alright I'll give you that one. Pelor knows how many times I've posted from work or carpooling on my phone.