Weak swim endurance

Ever since doing a nonstop 25M swim, I've been a bit more hopeful with my swim sessions.  After two sessions so far this week, I find I have no endurance when swimming.

For the week, I did a quick shoulder workout on Saturday and hit the pool Sunday.  I don't know if it was the lack of rest between my shoulders workout or if it was because I was showing off my airborned dynamic pushups and one-armed pushups about 30 minutes prior to swimming, but I tightened my right shoulder.  It feels like a minor strain and seems to be around the upper outer pectoral muscle or the lower trap.  It only bothers me when I reach my right arm across my chest to the left or sometimes when I lift my arm.  Not good.  This was Sunday night.  Monday, I did another indoor bike/run brick, then I swam again last night.  Good thing was the affected area doesn't really affect my swimming, but my lack of endurance definitely does.

I can't seem to do more than 25M at a time.  I need to work on making my technique more efficient.  I also need to increase my endurance by a lot.  The pool for the race is 25M and goes from 3 feet deep to 9 feet.  This means I also need to work on not relying on my feet being able to touch the bottom.  I'm thinking I need to at least be able to swim 50M nonstop and rest at the edges.  That or learn to pace myself better in the water so I can last 250M.  This would mean getting more comfortable in the water and learning to breathe effortlessly during the slow swim.

I'm going to try to hit the pool three times a week for the last two weeks to see if I can squeeze in some last-minute improvement.  I'm probably going to stop my shoulder workouts as well to prevent hurting myself.  My goal for the rest of this week is to run one more time and swim 1 - 2 more times.  Also, need to rest up and hope this tightness/strain goes away.  Oy.  It's almost funny to think that I've went from a non-runner to someone that looks at my 4 mile run tonight and think, "Oh good, an easy day."