Yes, fareastdriver, on the model of ADELT I'm familiar with, it should be deployed, if possible, immediatly before ditching, if not, ejection will be automatically commanded by water sensitive sensors. (as long as the arming selector is positioned on "arm deploy") Distress signals are activated by the upright position of the floating device.
On the above picture, the "ADELT" seems to still be attached to the airframe.
But of course, we still can activate it from inside the cockpit, when it is still in place.