The Lustica Peninsula consistently offers the clearest water on the Montenegrin coast. Zanjic and Mirista are both pebble coves with turquoise, transparent water — their relative remoteness means less boat traffic and fewer people, which helps keep the sea pristine. Queen's Beach (Kraljicina Plaza) near Sveti Stefan is also stunning and famously photogenic, though part of it is privately managed and may require a fee to access.
Along the Budva Riviera, Mogren beach — a pair of coves reached by a short clifftop path from Budva old town — has very clear water and a dramatic setting. The beaches around Petrovac, including the small bay at Lucice, are also known for good water quality.
For the most vivid colours, visit on a sunny day before midday when the light hits the water at the right angle. Pebble beaches almost always have clearer water than sandy ones because there's no sediment to churn up.