Total Immersion encourages swimmers to spear deeper than they are used to in order to set up for a great catch. But a deeper arm spear also helps drive more rotation. Playing with it today during a 1000m warm up (having watched the Phelps drills on my Facebook page), I immediately dropped back to 41SPL in the 50m pool. I really enjoyed the feeling of extra forward momentum.
This is defintiely a area wetsuit swimming can get in the way of as an arm in neoprene (no matter how thin the wetsuit) has a tendency to want to float on or near the surface of the water more.
I am a certified level 3.0 Total Immersion Swim Coach.