So completely unlike an octopus.>it gives him buoyancy
Buoyant force is proportional to the volume of the water the hair occupies. Because of how thin his hair is, the volume it occupies is minimal. Unless the hair so much less dense than Bortz itself that it compensates for this fact, it will have at most a marginal impact on Bortz's swimming ability.>large flat surface lets you glide in the water
Yeah if Bortz literally rides on his hair (which he doesn't, btw). Strictly speaking the buoyant force will act differently point-wise on Bortz's hair; a much greater buoyant effect takes place at the tip of the hair than at the root, and this causes a net torque on Bortz. Given that the work done by the total buoyant force is fixed at each depth below sea level (conservation of energy), the energy for lift generated by the buoyant force is sapped away by the rotational energy due to the torque. In other words, there is much less lift generated by Bortz's hair at any given moment than you think.>at the least undulate his head
Yes, but think about the length of the moment arm, namely the length of Bortz's neck. The amplitude of the hair's oscillation/undulation is proportional to this moment arm, and hence so is the energy generated for forward motion (I'm being generous here since some of that energy will go into changing Bortz's direction of motion). Unless Bortz is a giraffe (he isn't, btw) this is, again, marginal at best.