Pontikonisi is a nice place to stay right on the water near Corfu. Access to swimming is available right from the property, but be warned - they do NOT provide towels for you to go swimming! Expect to buy towels for 14 Euros if you want to hop in the water.
While the hotel has a roof garden bar, they no longer serve meals (other than bar snacks). There are, however, at least three very nice restaurants within a ten minute walk from Pontikonisi.
The biggest drawback is that it is right under the final approach path to Corfu airport, which is very busy. If airplane noise is a concern, you would be best to look elsewhere.