Nager entre deux eaux = (lit.) To swim under water; (fig.) To run with the hare and hunt with the hounds.
Faire eau (of boats) = To spring a leak.
Faire de l’eau (of boats) = To take in fresh water.
Laissez couler l’eau = Do not be anxious about what cannot be helped; Don’t cry over spilt milk.
Cela s’en est allé en eau de boudin = That collapsed utterly, came to nothing.
[The more correct form is s’en aller en aune de boudin, alluding to Perrault’s tale of Les Souhaits Ridicules.]
Échapper
Ce mot m’est échappé = That word escaped me inadvertently (i.e., I did not mean to say it).
Ce mot m’a échappé = I have forgotten that word.