You can start your essay with something like, "last holiday, i was visiting my uncle in Langkawi. And u can write about how did u go there, and how u greet your uncle. u can also write about stuffs that u do the first and second day staying there. just write stuff like u go visit some interesting places that your uncle brought u to visit. Then just add some relevant points in your essay. So at the end, just write that you and your uncle went to the beach, and someone tried to grab your uncle's wallet, and you tried to help your uncle but the bad guy was strong so he pushed you and your uncle and both of you fell in the sea. and some nearby people saw what happened and tried to help and some of them called the police. and just add up that you feel grateful bcs you & your uncle is safe and not injured.
p/s: it doesn't really make sense that the guy jahat and tolak both of you and you fell in the sea. i mean why would someone push u so u could fall in the sea? so dramatic.