Plaia Kalki is one of the best shore dives. Easy access, short swim, great reef. Also, probably it is close to the North tip of the island, you may see something you won't see elsewhere. Two weeks ago, this is the only site we saw sargassum triggerfish and large barracudas. Both directions to explore are good, but mind the currents.
Also, if you sign up with them, dive from the All West "inside diveshop" and explore to the South. Their reef does not look that great but it is packed with life. On one dive there, I counted 2 green and 5 gray morays. On another dive at night, I counted 6 clinging crabs. And they have resident lobsters under the little cliff right at the entrance.