Maybe I'm just dense...
I'm trying to improve my front crawl but bloody hell it's hard work. I'm reasonably fit from the bike (normally in top 3rd of leaderboards on Strava etc) and have ran half marathons etc. but I always seem to run out of steam after 3-4 lengths at a time. The problem is I can't swim slowly doing front crawl.
The local pool has a load of good swimmers and I'm fascinated by the portly 50+ gents who just seem to chug away for hours. Clearly, they spend a lot of time in the pool and have a better technique as a result. Any tips or online resources you've found helpful?