Where do you kayak? I scuba dive in warm waters with a rash guard and shorts or maybe a 3mm vest. My dive gear for Seattle is a drysuit with multiple layers inside. Please do not underestimate the thermal conductivity of water. The bad news is that cold also slows your decision making leading to making more stupid decisions.
In this particular case, they are showing people kayaking with shirts, shorts and a PFD around San Juan islands - notorious currents, water channels through a narrow inlet and water is really cold year around. If they had shown the same people with same gear in a Caribbean location, it would have been ok. And the other person kayaking in alpine lakes with a thick jacket is even more crazy. When (not if) you fall in, it gets water logged and pulls you down.
In this particular case, they are showing people kayaking with shirts, shorts and a PFD around San Juan islands - notorious currents, water channels through a narrow inlet and water is really cold year around. If they had shown the same people with same gear in a Caribbean location, it would have been ok. And the other person kayaking in alpine lakes with a thick jacket is even more crazy. When (not if) you fall in, it gets water logged and pulls you down.