Anonymous wrote:ask the instructor if there is amore advanced class or move to a faster lane. sounds like you are stuck behind some slow horses on a trail ride. you should feel drained after your workout.
NP: I swam with masters teams off and on in my 20s and 30s, and after a hard practice, I felt over the top energized. I was tired, sure, but stretched out and invigorated like no one's business. I'm usually a runner, but never had the aches and pains with swimming that I do with running (or rowing, my other sport of choice).
Give it time, OP. You do have to swim pretty hard to get the endorphins, but they're great when they're there. Do focus on form, though--it's hard to go fast without it.