I grew up on the Pacific coast, played in waves and body-surfed as a kid. The further the water receded after a wave crashed on the shore, the bigger the wave that would follow it. I think that if I was on the beach and saw the water pulling back at such an extreme rate, I would instinctively run like hell to get away from the beach and to the highest ground possible. Sounds like these gypsy folks had that one down.
"I have lived on the water all my life, and I have on numerous occasion seen very very low tides, but I have never seen a tsunami. 20/20 hind sight isn't really all that cool."
Tides sneak out. Tidal waves rush out. You would see it as a very strange thing, and either be mesmerized or running.