triangles can represent any sort of trilogy. Body-mind-spirit; any three people that relate;
Classically, the triangle with a flat base (as apposed to the upside-down triangle) refers to masculinity (the other femininity). In Jewish tradition it represents prayer or the direction of communication from man to God (the other being revelation, or God speaking to man - the combination of which creates the Star of David)
Squares indicate structure and order. Anything that is grouped in fours - the four corners of the earth; four suits in a deck of cards. Squares have also been a sign of femininity as well.
The water symbol (if it is water) has obvious connotations of cleanliness. Water is also a polar molecule which attracts itself.
The symbol in its entirety has a broad range of possible meanings from the three phases of water (evaporation, condensation, presipitation) to something completely personal that only has meaning to you, so something profoundly universal like the need for both men and women to become clean. Or none of these :)
And that's really what makes symbols so much fun.