Ok - got it. You're swimming against some current. If you are swimming salt water (ocean) and with a wetsuit, you are probably bobbing like a cork, or what my coach colleagues/friends down-under would say, "you float like a Sheila in that thing [wetsuit]" :-) But floating in a wetsuit, doesn't mean you are stable.
If sustaining 1.15 tempo at 18-20 spl that's actually a bit faster that 22-23 @1.0 - stick with the tempo that is the least effort holding you at your sub 2 min pace.
When you swim in the pool, can you easily hold 18 spl at 1.15 tempo? Say for 20-30 100m repeats?
Lastly, what's your height?