Based on our experiences of Iona last year, the two weaknesses in the design seem to be that at times the "overspill thingy" filled up faster than it could drain, so if there was much movement in the ship then the water rolled up the nice conveniently-angled glass ramp and onto the balconies with a big splosh (especially from the corners if the ship rolled side to side) and that if someone was happily splashing water over the glass pool wall and managed to hit the right diagonal angle, there's not enough distance between the corner of the pool (on the right hand side of photo above) and the side of of the overflow to stop the water overshooting the overspill tray. We saw one little monkey who discovered this loophole and was making the most of it until a staff member caught up with him!