There are a number of boats that stow the pole on the mast. HR is one. The upper end is secured to a track on the mast. It comes lose only deliberately for removal etc. The pole has a hoist line allowing it to be lowered or raised under control to set the proper angle for spinnaker or jib (as whisker pole)
The outboard (lower) end attaches to a bail at the base of the mast when stowed. Once stowed it is fully secured. Ours has had the green water test a number of times.
Same kind of setup on the Oyster I sail offshore on. Conventional-ish topping lift to the middle of the pole, but the mast end height is also controllable. When the pole goes away the mast end goes up, topping lift eased, and then the outboard end of the pole clips into a ring at the base of the mast. Haul the mast end tight, remove the topping lift (or not, depending) and you're done. Easy stuff, boat had seen way more than its share of green water, no problems