Ripples and Pebbles

Among the many ways to communicate silently, such as sign, telepathy and even written word. There is a talent for it only used by a few.
The Sui'ine are water bearers from all over the world. Children of the the water spirits from the realm of the Aquan people.
Sui'ine learn the that the ripples in a pond a can be created in many variations. So much so an alphabet of sorts was determined.
Once created the Sui'ine taught it to the merfolk who in turn passed it on to the Siren and Kelpie.
The premise being that those on land can see the ripples from above the surface of the water and interpretive what they mean and those looking from beneath can do the same.
This gives a sort of accent to the communication for beneath and above makings. It took into account shorter ripples, the length of time a ripple was left to die out.
Number of ripples made in quick succession or was it just one needed to get the words along. Truly a patient art of communication but it was silent and unique enough to only be known by a few.
During the battle of Esgilthas, when the Siren and Kelpie of Toan were hunted and those of a dark heart looked to rid the world of the water fey.
The language of ripples evolved into the use of certain pebbles, the size and type of stone meant different things. This helped with punctuation and volume. 
Still silent but it was now easier to add urgency to the words or the act of whispering. A concept those failed at first time around learning the language, always confused about how to drop a pebble quietly.
Being able to communicate in this silent way saved so many of the Fey, helping them avoid the hunters in their home and make it to safer lands.