Did not the post say they 'waved' down a commercial dive boat? In that context I also supposed that the boat changed course thinking that the divers were in distress to render assistance, but when the divers descended the operator took offense that they were exercised for nothing. Most commercial boats I have worked with cover this in the brief, that if you wave to me I am going to come-a-running, and if it is a case of mistaken signalling on your part, we're gonna have a talk. But a logical question is, if you are a bobbing head and see a vessel on a close-aboard approach inbound to your position, what are you supposed to do to signal/ attempt to get the craft's attention? I think most bobbing heads short on time would instinctively wave like crazy. Low probability of flashing the OK signal- a nonsensical signal in that situation. So they accept the dive boat's one-finger salute, but logically, that's probably why it was rendered. Because they said "I am in distress" and the folks on the boat weren't savvy enough to figure out-- "they waved because I was sort of heading towards them, and they were concerned, maybe even distressed."