This afternoon while taking a nap I experienced the vibrations multiple times. Each time the vibrations were brought on by getting involved in the same hypnogogic scenario. The scenario involved diving and whales. I seemed to have knowledge of a group who went diving, but their equipment would only let them go a certain depth. While diving, a whale would bite a diver and drag it down below this depth. The whale was only being playful, but the consequences of going below this depth were potentially serious.
This produced concern in me and the vibrations. It was almost like the deeper the whale went, the greater the vibrations.
It's interesting how while meditating, sleeping or projecting, certain images are brought to us. Sometimes they are in the form of clairvoyance, but instead of the really significant, fateful kind, sometimes they are just incidental.
I just posted an experience where I was given some imagery while in the Astral/3d Void, but it was simply a child's toy I would see later that day.
Another time I had an astral projection to place I would later on have a job interview at. It was a place I had never been to before, nor passed through. I thought for sure this was my clairvoyance telling me that I was destined to get the job, but I ended up getting a rejection letter. :(
In other words, it was incidental in the sense that I projected to a place I would be visiting in the future, but it wasn't any more significant than that.
On another note, perhaps you are destined to become a free diver. Have you ever heard of free diving? You probably have, but for those who don't know, people go down several feet and go back up, all while holding their breath.
Perhaps there is a freediving group that had a problem with a whale, or maybe the whale represents a malfunctioning weighted sled (a tool sometimes used to help one descend).