You may use a Tempo Trainer to challenge your control and movement in slower-than-normal motion.
You do this by gradually decreasing the tempo, until your stroke becomes uncomfortably slow. When you are forced to make the movements very slowly and count strokes to measure, it can expose weaknesses in your balance, stability and streamline that you may not notice easily when moving at normal and faster tempos.
When you first start slowing tempos away from your comfortable tempo (TC) you may immediately start lowering your stroke count (SPL). But at some point in decreased tempo you may not be able to lower SPL further. If you are near 1.80 then it is possible that you have reached some limit for your acceleration per stroke – a matter of power. But if you are short of 1.80 and cannot lengthen your stroke even with extra slide-time per stroke then you may consider where your form is breaking down and causing you to travel less than you may be capable of.
This chart gives you some idea of how we might evaluate a swimmer’s tempo. There are a lot of factors that may influence what is appropriate for you as an individual in your situation, but in general, slow tempos are slower than 1.50 and fast tempos are faster than 1.00. Tempos slower than 1.80 and faster than 0.50 may be nearly impractical for any human because of the physics and physiology of moving in water.