We're in a marina with potable water but it has a strong chemical taste. After looking around we came across the Brita 'On Tap' filter. This filter system has a tap adapter and you can select filtered water or just let water flow normally. It cost just over 35 euros with one filter (supplied) claiming to last for up to 1200 litres. It is important to note that it
does not remove harmful bacteria etc. - you have to start with 'clean' water. I can say with some satisfaction that the filtered water is tasteless.
There is a down-side. The way the freshwater pump works means that the filter operation can be slow, waiting for the pressure to drop enough to trigger the pump to work, then slowing again once pressure has been restored. However, it beats carrying the large water bottles from the supermarket
Time will also tell how long the filter really lasts