La Flottille is a restaurant on the northern arm of the Grand Canal, the only proper restaurant within the palace grounds themselves. The location is genuinely beautiful: tables look out over the water, with swans and occasional rowing boats passing, and the perspective back toward the palace is excellent.
The cooking is competent tourist French — salads, croque-monsieurs, plats du jour, ice cream. Don't expect a great meal, but do expect a pleasant one in a setting you will not find anywhere else. The prices are higher than equivalent food in town, but you are paying for the view and the convenience.
It is worth stopping here for a drink if not a full meal — a glass of wine or a coffee while watching the canal in the afternoon sun. If you are hiring rowing boats (the hire point is nearby), La Flottille is a good place to begin or end that part of the day.