I also have a Lab and she loves, loves the water. She is also OCD and when she does something she likes she does not or cannot stop. I got her a lifejacket and I don't worry about her drowning anymore. I put in on her at home several times before going into the water, getting her used to wearing something that is thicker and heavier then a Thundershirt or Tshirt. Sasha did really well with the jacket but I do not put it on her all of the time.
It Is What It Is