Looking for info on ppl who have life jackets for dogs

So my smaller beagle/dachshund mix absolutely LOVES to go swimming. We take him with us to the river and turn him loose while we ride the horses. He goes about and swims like the little champ he is and happily rolls in the sand after. He is getting older now and seems to get tired a lot quicker. We plan on going to the river some more once summer comes around again. I'm worried about him getting tired in the middle of the river and going under. I've been looking at those little life jackets for boat dogs but I feel like those are more for dogs who might accidentally fall in. What about for dogs who swim? Would that still help? Thanks for any advice! <3