The head is probably the most important element of your swim stroke - basically the body will follow whatever the head does: over turn the head during the breathing, you will over rotate the body; keep the head up too high, you will lower the legs.
Tim is a newcomer to the sea swimming scene and - hats off - has done the LCW weekend half distance swim and embarked on his training for the full distance swim next year!
On this assessment session we saw how his legs are clearly causing excessive drag in the water, which is mostly caused by his head position in the stroke.
Tim was sighting quite frequently, not necessarily a bad thing in open water, but sighting is a whole technique in its own right, and this frequent sighting had the effect of keeping the head raised too high, which in turn lowered his legs.
Upper body / back flexibility and strength training is required to counter act the effect of raising the head, something that water polo players train for years to achieve.
The effect in most cases will be that the legs are spread as well to sub consciously stop them from sinking.
The effect of the lowered leg angle and spread leags and knees is a drastic increase in resistance moving through the water on areas like the thighs, knees, calves and heels.
It's important to keep your legs together, straighten the legs but keep the knees flexible on the kick, kick from the hip and keep the legs raised so the heels just break the surface of the water.