Predicting an approaching tsunami looking at the beach?

I remember hearing a story after the boxing day tsunami (2004) of a young girl and her mother who were on a beach that was later to be devastated by the tsunami. The young girl said that she spotted something in the sand or something about how the sand was acting that she had learned at school meant that a tsunami was approaching. The girl told her mother and the two left the beach straight away, certainly saving their lives.

My question is, what did the little girl see that alerted her to the approaching tsunami? I imagine it has something to do with the earthquake causing disruption in the sand but I would like to know the straight dope.

Receeding water. Oftentimes (but not always) the water receeds substantially.

Her name was Tilly Smith , BTW.

And here is link to BBC article about her.

Does anybody have a picture of what the “frothing bubbles on the surface of the sea” look like? And how quickly does the sea receed? Is it a slow affair that could be mistaken for the tide or is it very dramatic and unmistakable for anything else?

The Wikipedia article links to an article by The National Geographic that describes what Tilly observed in more detail. I would say there is no mistaking it for anything else.

it is a remarkable receding. enough that most people will remark: “whoa nelly, look at that!” then people look instead of run.

thankfully, miss smith, knew to remark and run.

There is home video of the receding water (I caught a bit of it on the Discovery Channel). You see a bunch of tourists saying “Damn, honey, where did all the water go?” and “Hey, where are the hotel staff going?” Then a guy walks up, takes one look and starts telling people to RUN to higher ground.

If the water recedes suddenly, run like hell.