Al borde de

[ROBINDESBOIS]

Estar. Sentado al borde de la piscina, chapoteando los pies.
English?

[JPablo]

I'd think, "Sitting at the side of the pool, splashing /dabbling with your feet"... (Let's see what natives have to say...)

"Al borde de" would have these translations,
on the verge of, on the brink of, at the side of, on the edge of.

For "al borde de un ataque de nervios" I'd tend to use "on the verge of a nervous breakdown"... or some such.

[wrholt]

I'd say this as: "sitting on the edge of the pool dabbling your feet (in the water)/splashing (the water) with your feet".

"Sitting by the edge" implies that you are sitting somewhere relatively near the edge of the pool, either on the ground or on some piece of furniture, and your legs are most likely NOT hanging over the edge.

"Sitting on the edge" implies that you are sitting directly on the ground and you are close enough to the edge that you can hang your legs over the edge if you wish to.

One dabbles something (a body part) in a liquid (water).
One splashes a liquid (water) with a tool (feet).

[ROBINDESBOIS]

Perfect , thank you.