No.
You need to do drills just grinding lengths at some point becomes prohibative, try doing a pyramid set
No more than 20sec rest after each
25m -100% Effort
Rest
50m 75%
Rest
100m 50%
Rest
200m Easy
Rest
100m 50%
Rest
50m 75%
Rest
25m 100%
8x25m rest 20sec at each 25, important to be consistant on the 25 aim for 22/23 seconds as a starter
Rest 1min
Then repeat the pyramid set.
Cooldown include backstroke to open the chest up.
The goal is to get your 8x25 set below 20 seconds ideally, this should improve your endurance which will improve your current times and then after 4 weeks drop in the 8 x 25 as 4 x 50, build slow and do not forget to breathe
My one does too so I'm expecting that to make a difference too.
Nice one. My mate who convinced me to do this tri finds swimming easy too, he does 5k fairly regularly but doesn't like the long cycles/runs. Ironman is a hell of a feat. One for the bucket list though