Yes, it's summer. Yes, many people find a life jacket or a personal flotation device (PFD) to be hot or uncomfortable. Tough noogies. I'm going to repeat the advice that is frequently given to kayakers and to people out in canoes, rowboats, dinghies, and other small boats: a life jacket can't do you much good when you are not wearing it.
Oh, sure, a PFD can make a good cushion under your butt. The answer to that is to make a proper cushion for your butt, or to carry a second PFD to use as a cushion. It is darned nice when floating beside an overturned boat, collecting one's sense of aplomb, to have a cushion or spare PFD to hang onto -- but it's even nicer to be WEARING a PFD and holding onto that floating cushion.
Oh, sure, a PFD can make a person feel hot on a sunny day, or it can restrict some people's feeling of free movement. That's why I wear a Kokatat Orbit -- it doesn't make me feel constricted or wrapped up tightly. Even better is the Mustang style of inflatable PFD which has no lift until inflated, or the SeaO2 which has a little lift until inflated, and then it has way more lift than an ordinary PFD.
But after all the excuses, wear your PFD to make it easier for the search party to find you. Most of the recreational fishermen who are found drowned are a few feet away from their boats, where their life jackets are stuffed behind the seat along with a mickey or a six-pack.
I like the news that the Canadian regulations for stand-up-paddleboards are considering allowing paddlers not to wear a PFD if they are wearing a leash attaching them to the board. Regulations aren't just arbitrary rules -- they are rules meant to reflect what people are doing and how they can be safer.
Nobody plans to add a fatal accident to a fun outing on the water. Nobody wants to be part of a search party dragging a lake. And nobody wants to be hiring this couple with an underwater robot, even if it is pretty darned cool and is put to good use.