I needed a cost affective towable kayak bait tank.   I had used a bucket and a battery operated air pump but since fish release ammonia, they still didn't last long.  Keeping the bait in the water is likely the best approach for a kayak. 

Since I had left over vinyl fence post (5"x5") from another project (Home Depot), I felt I could use that as a ‘body’ to keep the printing time and costs down.

I modeled the parts in Fusion 360 and need to focus on water flow (holes in the nose and rear) while keeping in mind the hydrodynamics.  I use a 2.3 hp engine, and I don't plan to tow this at max speed.

Since vinyl and PVC doesn't float, the fins are added which I printed at 10% infill for buoyancy.   It floats on the surface which is fine for me.  

The eyes, smile and whale tail are strictly for ‘fun’.

I attached the the fins and the other parts to the vinyl tube using 3/16" x ½" aluminum pop rivets from Harbor Freight.

The dorsal latch uses a 32mm M6 stainless steel bolt with 2 nuts.  1 nut to secure the bolt in place on the tube, while the other is inserted in the top of the dorsal.

I drilled a hole in the nose and attach a ¼" line with a knot.

My printing costs are for everything is about $15.

I haven't tried it yet so stay tuned for adjustments.