Pichus are known to randomly discharge electricity when startled.
Well the artist did not draw it, so people are free to interpret their own outcome. Ippers is not exactly prone to electrocution paralysis and drowning, so I will assume everyone just had a good time at the pool and in the event of accidental electrical discharges, it was nothing more than a shocking jolt, similar to that of a rascal in the pool, splashing water in your face.