how can i teach the synonyms ‘dive & jump’ more efficienctly?
‘Dive’ has the sense of going headfirst, while ‘jump’ just means to move up and/or forward.
If I dive in the water, I’m going headfirst. If I jump in the water, any part of me could hit the water first.
Does that help?
So the expression “she dove/dived headfirst into the…” would be redundant, right?
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Generally speaking, if you dive into the water, the only part(s) of your body that might hit the water before your head does would be your hands and (fore)arms. Of course, there is something known as a “belly flop”, but I don’t consider that to be a “proper” sort of dive. 
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thank you very much for having given me a very precious answer to the question: what’s the difference between ‘dive into the water’ and 'jump into the water."
What do you think of these examples?
In November of 2007 I re-located back to the east coast to be near my beautiful wife, and dove feet first into photography.
In the 36th minute, Barrett received a beautiful leading pass from Blanco but his shot on the left side, inside of the New York penalty area, was easily stopped by Waterreus as the Red Bulls 'keeper dove feet first to knock the ball away.
redbull.newyork.mlsnet.com/news/ … &team=t107
As she got into high school her parents enrolled her in voice lessons, where she dove feet first into a career in classical music.
google.es/search?hl=en&q=%22 … gle+Search
Although I have seen them on the Delaware River and at John Heinz National Wildlife Refuge, this was the first I’ve seen over the Schuylkill in Philadelphia. The osprey flew further downstream and dove feet first into the river and caught a fish. It immediately flew into some trees where I lost sight of it.