Subsea tool assembly and method of operating a subsea tool

A subsea tool assembly 10 including a package 20 that houses a tool control device for controlling operation of a subsea tool 14, a controller configured to selectively operate the tool control device, an acoustic communication node configured to receive and transmit acoustic signals through a tubular body of a subsea string 12, and an electrical power source for powering them. The controller is configured to decode acoustic control signals received by the acoustic communication node and selectively operate the tool control device in response. The tool control device may be an accumulator and the controller may operate a solenoid valve to release pressure from the accumulator to operate a landing string. Sensors may be provided on assembly to provide information about the operation of assembly. The tool enables full control of a subsea tool with operational feedback without the use of an umbilical.