Ferry ride to Poros from Aegina takes about 1.5 hrs via the regular ferry Apollon Hellas (from the Saronic Ferries Company).
Two adults + 1 kid one-way tickets cost 22.80 Euro.
This route stops at Methana Island before proceeding to Poros Island.
There's hardly any taxi waiting at the port area. We waited for quite a bit to find one.
However, there is a free minibus the runs along the harbourfront that might be able to take you closer to your hotel. We just didn't know about it that time.
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