The three Celtic elements are Earth, Sea, and Sky.
The Celtic trad is rife with trinity symbols.
They also represent the three stages of life of both male and female.
Male-youth, warrior, wise elder
Female-maiden, mother, crone (see also the trip moon symbol)
The Mabinogian lists 33 triads.

A triad of my faves-
The three emotions that come uninvited: fear, jealousy, and love.
The three teachers who impart wisdom: suffering thought and a truthful heart.
The three most beautiful things in the world: a ship under full sail, a woman with child, and a full moon.
I definitely think a trinity symbol is the way to go with your tat.
My next one is going to be a trip moon around my belly button with a design around it that will probably end up covering most of my belly.
