I guess it really doesn't say it, but I had always assumed that if you can breath under water you can speak and cast spells under water.
1) By RAW does Water Breathing allow you to speak?
2) By RAW does Water Breathing allow you to cast spells with verbal components?
Yes and yes. This has been true (and never really clearly stated) since 3rd edition. Nothing has changed that.
From the PFSRD section on underwater terrain. Bolding is mine
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.
Thanks guys.
That's what I was thinking, but I wasn't sure.