Wikia

Tidal Waves
Tidal Waves (Passive) Passive When you cast Chain Heal or Riptide, you gain the Tidal Waves effect, which reduces the cast time of your Healing Wave and Greater Healing Wave spells by 30% and increases the critical effect chance of your Healing Surge spell by 30%. 2 charges.
Usable by
Class	Shaman
Properties
Type	Utility
School	Physical
Talents
Specialization	Restoration
Level required	50
Related buff
Magic Tidal Waves Cast time of next Healing Wave or Greater Healing Wave reduced by 30%. Critical effect chance of next Healing Surge increased by 30%. Duration: 15 seconds

Tidal Waves is a passive shaman ability learned at level 50 for those with the restoration specialization. After casting [Chain Heal] or [Riptide], the cast time of [Healing Wave] and [Greater Healing Wave] is reduced, while the crit chance of [Healing Surge] is increased.

Tips

When healing a single target, Tidal Waves allows you to briefly increase your healing output by casting Riptide followed by two fast Healing Waves or Greater Healing Waves. This can help you overcome damage spikes on tanks, or help you or an ally survive in PvP.
When using Chain Heal to heal a raid group, Tidal Waves allows you to cast a quick Healing Wave or Greater Healing Wave on a target that needs immediate healing. The reduced casting time of the heals not only means that a potentially life-saving heal can land faster, but also that you can get back to casting Chain Heal sooner.

Patch 3.2.0 (04-Aug-2009): No longer reduces the cast time of Lesser Healing Wave by 30%. It instead now provides +25% critical strike chance to Lesser Healing Wave, along with the previous 30% cast time benefit to Healing Wave.
Hotfix (2009-04-22): "The Thunderfall Totem will no longer increase the casting time of Healing Wave or Lesser Healing Wave when Tidal Waves is active."
Patch 3.0.3 (04-Nov-2008): Will now also proc from Riptide. Number of charges increased from 1 to 2.
/ Patch 3.0.2 (14-Oct-2008): Added.