Flow Like Water is a great card that was released at the right time, as Protection now offers a number of events that are usable.
At the time of my writing of this review, the following events are usable with Flow Like Water:
Defiance (0 cost)
Desperate Defense (0 cost)
Expert Defense (0 cost)
Never Back Down (1 cost)
Preemptive Strike (1 cost)
Shield Spell (o cost)
Sidestep (1 cost)
Flow Like Water is an important card as it supports both of the major Protection Archetypes that I enjoy: Defender (wants to actively defend every turn and trigger upgrades) and Dodger (plays cards to reduce damage without actively defending). It also addresses one of the key issues with Protection: damage. This card provides a very useful ping, as extra sources of damage are always welcome, removing those annoying Tough cards wihtout wasting damage.
It's still not a perfect card. Defenders don't usually take Expert Defense since they want Desperate Defense's ready. It doesn't trigger off if Indomitable, a defender staple. It gets into the way of playing the set of Upgrades you need to get on the table (Unflappable, Armored Vest, Electrostatic Armor, Hard to Ignore), A couple Dodge staples (Deflection and Subdue) don't work either, as they are missing the (defense) tag.
Still, an early Flow Like Water will probably mean 8 or 10 easy damage throughout the game, boosting every (defense) card in your deck. It requires some thoughfulness for inclusion, but if you have the Events it will always pay off. You were going to play those Events anyways, right? But now every card does a little extra.
My rating is a B : Effective in a range of builds