Where is this rule that says spells can't be cast into water?

[Game Master]

In the Melee Tactics Toolbox, there is a new feat which says the following:

Quote:

An aquatic spell functions normally when

underwater and requires no caster level check to cast, even
if it possesses the fire descriptor. In addition, the spell can
be cast from the surface into water and still be effective.
An aquatic spell uses up a spell slot 1 level higher than the
spell’s actual level.

I've been told before that spells can't enter the surface of water, but I looked and looked for this ruling and never found it.

Can anyone give me a page number?

[RainyDayNinja]

PRD, Underwater Combat wrote:

A completely submerged creature has total cover against opponents on land unless those opponents have freedom of movement effects. Magical effects are unaffected except for those that require attack rolls (which are treated like any other effects) and fire effects.

So it sounds like it would negate the cover for spells requiring a ranged touch attack.

[Marc Radle]

Aquatic Terrain

Lots of good stuff there.

Of note:

Spellcasting Underwater: Casting spells while submerged can be difficult for those who cannot breathe underwater. A creature that cannot breathe water must make a concentration check (DC 15 + spell level) to cast a spell underwater (this is in addition to the caster level check to successfully cast a fire spell underwater). Creatures that can breathe water are unaffected and can cast spells normally. Some spells might function differently underwater, subject to GM discretion.

Fire: Spells or spell-like effects with the fire descriptor are ineffective underwater unless the caster makes a caster level check (DC 20 + spell level). If the check succeeds, the spell creates a bubble of steam instead of its usual fiery effect, but otherwise the spell works as described. A supernatural fire effect is ineffective underwater unless its description states otherwise. The surface of a body of water blocks line of effect for any fire spell. If the caster has made the caster level check to make the fire spell usable underwater, the surface still blocks the spell's line of effect.

I did a fair amount or research on the subject when I was writing The Sunken Pyramid. I actually compiled all the relevant under-water combat and spell-casting rules in an appendix to that book to make the GM's life a little easier ...

[Game Master]

Ok, good. Sounds like I was right in my initial understanding. Great!