The eastern harbour of Alexandria contains one of the most extraordinary submerged archaeological sites anywhere — the drowned royal quarter, including the foundations of Cleopatra's palace, fragments of the Lighthouse of Alexandria, and the entire small island of Antirhodos where the queen had her private residence. Most of the site sits in 4 to 8 metres of water; some elements are visible to snorkellers, but a dive is needed to see the larger statues and sphinxes.
A handful of operators run organised dive trips. Alexandra Dive (in Bahary) is the longest-running. Visibility ranges from poor (typical Mediterranean port silt) to surprisingly clear; winter and early spring are usually best. Two-tank dive trips cost around €80–100. Snorkelling trips are cheaper but show only the fringes. The Bibliotheca Alexandrina exhibits a number of artefacts recovered from the site — visiting both adds up to a coherent view of submerged Alexandria.