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The picture of your friend is shot at 1/160 yours seems to be shot at 1/60, the blue of his water is darker
His picture is also darker in the foreground and has more depth of field it is shot at F22
How was your picture taken?
While both photos were taken aimed upwards, your friend's also includes a sunburst giving it that extra sense of depth and drama. In many instances, a slight underexposure can really add an extra oomph to the saturation.
Close focus shots should be at 1/125 as a minimum actually more
None of the two shots is actually pointing upwards so the difference is the colour of water and the fact that you have the reef in the way which is bad as it also calls for the light to shine on white bits with sand
Try to get the top with water or get rid of the reef increasing speed to 1/500 assuming your flash still syncs?