Apparently there is supposed to be a sound for placing a boat in this snapshot, however placing a boat plays no sound at all!
Comments 4
They do now, see it for yourself in the patch notes on the wiki: http://minecraft.gamepedia.com/15w47b
As MC-93281 has been closed, could this ticket be reopened? Things like these are worth considering in isolation. Also keep in mind that armor stands, which are also an entity, have a placement sound, so this doesn't sound particularly far-fetched.
As I remember boats never had placing sound...