FISHIOLOGY

I've always been fascinated with the PBB var Turkana when I first laid my eyes on them in youtube. The thing about them is they swim, yes they swim like a regular fish unlike any lower jaw bichir you see. What intrigue me is why do they possessed this ability when the rest of the clan do not? Could it be because of the depth at lake Turkana or is there something else?  I've been studying the water and the lake with all possible information that I can find online. Polypterus Lapradei enjoys swimming. When the batch of Lapradei had successfully learned to controlled their buoyancy with their lung, they swim a lot, and swimming no longer becomes a struggle.  I was patiently waiting for a batch of wild caught PBB fry for more than a year but with no luck. Finally I bought a batch of captive breed Lapradei Fry at 3" for my experiment seeing them being the closest thing I can find. What I found about the water of lake Turkana surprises me, it is a salt lake,