In an article about the eldest locks of Rotterdam (in Dutch) I found a post card, taken more or less from the same viewpoint, the filename of the picture was "spuiwaterboot," so someone probably once took that filename as the name of the canal.

Yes, this is Rotterdam: The Spuiwater canal.

In my opinion this photo cannot be from Rotterdam, for the simple reason there has never been a canal with that name in Rotterdam. "Spuiwaterboot" is a strange name anyway, "water" meaning "water" in Dutch as well and "boot" meaning "boat". "Spui" used to be an old name for a water outlet (the best-known "Spui" is a now a square in Amsterdam). So most probably what we have here is a contamination of terms used to catalogue a photo showing the water of a canal named "Spui" with a boat in it.

The most probable candidate for this photo's location might be the Spui Canal in The Hague, which actually existed until being filled-up and changed into Spui Street between 1900-1905. In that case, this might be a photo that was made just before the canal was changed into a street.