Odysseus and the Phaeacians navigate through the Canali Stretti into the sound, which is basically endless since it opens into the Ionean Sea to the south, so it's hard to specify exactly how far they go. They may have already crossed the entire sound at the point when Homer writes:

......at the head of this harbour there is a large olive tree and at no distance a fine overarching cavern sacred to the nimphs who are called Naiads.

Once they reached the place of anchorage......

There's a huge cave, now called Papanikolis, as far as Meganisi (Taphos), which lies on the same length (or as Homer writes 'no distance') as the head of the harbours of Rouda Bay and Syvota Bay. See the blue line in the picture far left. These are the nearest harbours to the cave, together with another, smaller harbour at the 533 metres high Cape Lougi called Kypos, but let's take a closer look at the cave first.

Beyond the Sound

Only after navigating the sound do they come to the place of anchorage. Mainstream scholars have always believed that all items mentioned by Homer must have been within the same harbour, the harbour of return, but to me it reads like Phorkys must have been somewhere in the sound between the breach and the next point Homer mentions, the place of anchorage.

Still used for navigation

Odussey Book 13 line 101 Barry B Powell
Odyssey Book 13 line 101-103 Samuel Butler

Canali Stretti

Phorkys?

Phorkys?