Look at her eye sockets in orange bikini shot img_9323, then look at her eye sockets in blue bikini shot img_9065. Leaving for the moment that img_9065 is blurred, the point is that being in the sun for 9323 has left really dark shadows. You will see some people shooting in bright sun with flash, or big reflectors, to fill in those dark shadows. 9065 was shot at 1/100th, at 95 mm, according to EXIF data. I think her right knee is the sharpest thing in the photo so focus could have been off, but the shutter speed is slow enough that she may have been moving too. If you can't get someone completely in focus, make sure the eyes are in focus.
A couple of things to try out:
Set a single focus point to be active. Put that point on the near eye, press the shutter button half way and hold it. Recompose then press the shutter the rest of the way down.
Use a flash. Expose for your bright background to be slightly under exposed, and lock exposure, or shoot in manual. When the flash fires it will light your subject. Try ETTL mode, and also manual mode at part power. Observe the differences. In manual mode, adjust flash power up and down for a few shots. In the field, the camera's monitor can be deceiving due to ambient light, look at the histogram to see how the exposure is.