TidelinemacOS

Yes. A week of predictions for your saved stations is cached, so the menu bar keeps reading on a boat or in a valley. Surf forecasts need a connection and say so rather than showing you something stale.

Almost always because the board quotes a different station, sometimes miles away. Tap the reading to see which station you are on and how far it is from you.

From national hydrographic offices, refreshed every six hours, with the station and its last update shown at the bottom of the panel so you can always see how fresh a reading is.

Not by hand, but tell us the harbour and we will add it if there is a published station near enough to be honest about. Most requests are live within a fortnight.