Diving Behaviour in Egyptian Geese

Zoe and I went for a walk round the lakes yesterday evening.  Near the northwest corner of the large lake we saw the pair of Egyptian geese (Alopochen aegyptiacus) taking off over the water, and there was a third goose - one of their by now fairly mature goslings following them up into the air, and then further back the three other goslings flapping about desperately only to fall back back to the lake.  The parents and the first gosling turned back and alighted on the water again. 

Then one of the three unsuccessful goslings did something I have never seen an Egyptian goose do before: it dived under the water and resurfaced  a few seconds later 5 to 10 metres away.  Then some of the other goslings made similar dives.  I cannot remember if either of the parents made one of these dives but at least three of the four goslings definitely did.  I was stunned.  As I said, in the 20 years since I have known the Egyptian geese on these lakes, I have never seen them (or any other geese) do anything like this.  I can only speculate that one of the goslings must have seen a coot or a great crested grebe dive and come up with food, and thought it would do the same, and it caught on.