Try front crawl, but keep your head up and out of the water.
That forces you to arch your back and paddle more with your lats.
Similarly, doing the Superman position on the floor keeping your legs and feet together off the ground is good too.
Also get a set of bungee arm trainers like Power Strokers or Mavrex and a bar to do pull ups will help 👍
Replied on How to get in paddling shape when land-locked
08 Oct 04:26
Coryn Daniel As far as I can tell: https://mokanlife.com/products/the-mavrex