Any handheld, hand-pumped air supply is dangerous without training, don’t buy them — Instagram is showing a lot of ads for ‘hand-pumped scuba tanks’. There are a bunch of different brand names, all selling the same product. (Maybe from the same outsourced manufacturer.) These brands have names like: Scopel Scorkl Smaco Lung T MiniDive Whatever the brand name, don’t buy one, they are…