Those inks are also water-fugitive but they also offer a two-fold security feature:
they become fluorescent under UV light when they have been watered.
This type of inks is used in view of an  immediate revealing of the forgeries: if the printed document has been tampered with water, then, first the ink intensity will fade, and secondly when exposed under UV light, the fluorescence will be clearly visible.
When printed in dry offset or letterpress, the visible colour does not show any fluorescence but after the document has been tampered with water, the ink becomes fluorescent (mainly in blue) and the strongest effect will, of course, be achieved on non-bleached substrates.