If you're spending some time in Matecumbe, Bud n' Mary's Dive Center and Anne's Beach are top sights worth seeing.
Venetian Shores might not have many top sights, but Islamorada County Park and Founders Park are two attractions nearby that you can check out.
Though Lower Matecumbe Beach might not have many top sights, you can venture to the surrounding area to see attractions like Anne's Beach and Sunset Drive Beach.