What he means is to have less straight spots and try to use more "turns" to make it look more natural. The second attempt is a lot better, but there are some places that just look bad. The little green spots that have borders backed up back to back, with a little brown streak in the middle just looks bad.
I would look over the picture he posted a little more, and try to get some more inspiration to make the shape a little better. Also, in my opinion, I would use the other sand/water border. The one where the water actually looks like it is coming up on the sand.