Poros is a reasonably good place to stay overnight. But make sure you don’t moor your boat too closely to the ferry boat docking areas. The ferries create a lot of swelling, especially when sailing away. If there’s room, you can moor in the small fishing port. The harbour master will assign a mooring place upon entry. Drinking water is available on the wharf next to most mooring places. Although this port is used for sailing ferries, the adjacent beaches are very clean. The same applies to the sea water.
You can easily spot Poros from the north. From the south you won’t see it until you pass Ak Pronos. Watch out, the prevailing winds can be strong and there are strong gusts of wind from the coast.