Unless from a known reliable source here is why you can't trust customer reviews. This is a review on the Roka website
"I "was" a back of the pack swimmer. Just got my Viper Comp last week and wore it to the various places I swim. I am a"descent" swimmer that could use more kicking, less drag... my first Ironman race is in May 2016. I never ever imagined moving through the water (Ocean) that fast. Super amazed. It lifts my body making parallel with the Ocean floor, thus eliminating drag. And most amazing? I'm gliding through the water... I mean really smooth and somewhat appears to be effortless from my normal swim struggle. THANK YOU for the Viper Comp. A 1,000 meter open Ocean swim use to take me an avg of 40 minutes. Try 17 minutes now!!! May seem slow to some but it's quick a BIG improvement for me."
I highlighted/underline the appropriate section. Quite an improvement
"I "was" a back of the pack swimmer. Just got my Viper Comp last week and wore it to the various places I swim. I am a"descent" swimmer that could use more kicking, less drag... my first Ironman race is in May 2016. I never ever imagined moving through the water (Ocean) that fast. Super amazed. It lifts my body making parallel with the Ocean floor, thus eliminating drag. And most amazing? I'm gliding through the water... I mean really smooth and somewhat appears to be effortless from my normal swim struggle. THANK YOU for the Viper Comp. A 1,000 meter open Ocean swim use to take me an avg of 40 minutes. Try 17 minutes now!!! May seem slow to some but it's quick a BIG improvement for me."
I highlighted/underline the appropriate section. Quite an improvement