Timed release system. Buoy with 750 g buoyancy, square aluminium profile 25 x 25 mm with restricted end. Stone salt piece fitting in profile. Stone weight with cord and 1 cm round wood/medtal piece, hold by salt stone.
Styrofoam bear a spayload. On deployment in water the salt stone dissolves and releases the stone weight. test performed at 310 m water depth.
The buoy surfaced after 30 min ca. at approximately same position.
Styrofoam bear (right) compressed after deployment to 310 m water depth..