A smooth-bore nozzle on a well-settled supply throws a column that stays coherent for roughly the first two-thirds of its height and then breaks into droplets, which is what makes the top of a jet read white and the bottom read as glass. That break point is the design variable: shorten the settling length and the jet whitens earlier and looks softer; lengthen it and you get a hard, glassy column that reads as a line rather than a plume.
Height is roughly proportional to pressure and not to nozzle size — a 12 mm and a 20 mm bore at 2 bar reach within a few per cent of each other, but the 20 mm uses nearly three times the flow, and therefore three times the pump and three times the basin. Sizing a jet by its diameter rather than by its throw is the most common mistake we see on other people’s drawings.
It is loud, and the noise is on the way down, not the way up. Landing a 6 m jet in 150 mm of water gives a bright splash around 4 kHz; landing it in 400 mm of water over a pebble bed drops several decibels and moves the energy lower. Wind is the real limit: above about 5 m/s the column bends and the droplet cloud drifts, and the rule of thumb is that drift equals a third of the height at 7 m/s. Design the dry margin for that, or fit an anemometer and mean it.