There have been attempts at folding kayaks but lions believe a game changer would be a rigid kayak that folded in 2 like a folding bike.  The watertight joint would be the hard part. There could be 2 rigid halves bolting together without a watertight joint.  A flexible rubber skin would wrap around the entire assembled kayak.  The rubber would be the thing which folds up, but it wouldn't need any structural rigidity. 

The focus of this is just to make it fit in a vehicle rather than to be the most compact possible or the fastest to assemble.  The Oru kayaks are like a solution in search of a problem.  If the stiffness & the water tightness are provided by 2 different structures, the problem gets a lot easier.

It turns out most of the folding kayaks are a skin on frame design.  The goog only hit Oru for some reason.  Accessing the ocean requires a heavier one.  The only one with a working link is https://longhaulfoldingkayaks.com/

They're $5000.  All the ocean destinations have kayak rentals.  Only the small lakes don't.