History: Pisa a maritime power without sea harbour?

In the 12th and 13th century Pisa was a maritime power.

Surprising when you take in in to account that the city is around 15 KM land inward from the coast, connected by the river Arno.

Bruges (and Ghent Belgium) had a similar lay out to the sea via the river Zwin in the 14th and 15th century.

So it was possible in the past to be a maritime power without being located directly on the coast.

Is that still the case today?

What do you think?