Alien Abduction
A very similar phenomena is reported commonly among alien abduction cases, whereby people encounter unknown beings, shadows, and shapes of entities during the event. Unlike NDE reports, abductions often focus on experimentation toward the subject, at times in a very helpless and horrific manor.
Psychologists and Hypnotherapists have studied these phenomena extensively, they too have trouble (as their patients) to understand why it happens; Especially when they examine healthy individuals without any sort of preexisting condition. Some scientists believe the abduction phenomena can simply be attributed to a combination of mass influence and traumatic life events, yet believers have a very different outlook from the experience.
Perhaps what people witness during these strange encounters, in combination with cryptid creatures, is an example of afterlife spirits or entities from another realm attempting to make contact with us. Suppose we visited a distant planet in the universe with life flourishing upon the surface, and suppose that life was at the same point in scientific evolution as ourselves.
Going a step even further, imagine the species living on that world shared similar biological characteristics to our own. How would they react seeing us for the first time? Possibly slight variances in biological makeup would have us appear similar yet different enough, and the travel method to reach their planet may affect the space-time continuum, thus altering our appearance even more.
Apprehension tags along with human travel to distant reaches of the universe and with it follows precautionary methods of exploration. Reconnaissance is necessary, done devices become even more helpful, and new types of safe guards yet to be invented could change the playing field before any human is put into potentially dangerous situations. For example, developing a holographic reconnaissance vehicle capable of collecting environment data could be used to test the waters.
Perhaps such a vehicle is shaped similar to biological life forms re-con cameras picked up from the distance in order to find out first-hand what level of threat might be encountered - reminiscent of some Bigfoot reports, where the apparent creature vanishes completely when shot at. Safe exploration tactics will rely on the art of deception, to blend with foreign environments and any biological life present. Psychology definitely plays a role here and every last drop of intelligence can mean the difference between a successful encounter or a detrimental one.