Sticks out a great big hand and grabs me by the wrist

Does anyone want to help me out with the 80's (or maybe 70's) Doctor Who episode which featured a lot of grabbing hands appearing from unlikely places? Specifically, I remember a hand thrusting out of a water butt to grab the Doctor round the neck, and a series of hands trying to pull him down into a sandy beach.

Weirdly, I can't remember which Doctor. And my Google-fu appears to be failing.

spindlemere did once track this episode down for me, but I've forgotten his answer :(