Externally it was a bathysphere with its anchor weights removed; internally it much more nearly resembled some of the complicated barrels in which foolhardy exhibitionists have essayed the spectacular, useless trip over Niagara Falls.
Upon receipt and verification, the acoustic release triggers a mechanism that drops the anchor weight.
The function of the release mechanism is to open a gate to release an anchor line and attached anchor weight, which allows the now buoyant assembly to travel to the surface.
No current that's worth speaking of, no wind, a heavy anchor weight and a stout anchor rope.
Ultimately, he dismembers the bodies of his victims into several sections, wraps them and the plastic sheeting in biodegradable garbage bags, then adds rocks from the dock where he keeps his boat as anchor weight and seals them with duct tape.
Submerged moorings use an acoustic release that connects the mooring to an anchor weight on the sea floor.
Current meters are usually deployed within an oceanographic mooring consisting of an anchor weight on the ground, a mooring line with the instrument(s) connected to it and a floating device to keep the mooring line more or less vertical.
Docks's mud fudge pie is irredeemably rich yet, remarkably, not an anchor weight like most such concoctions.