Simple if pool alarm is triggered 4 mini pistons lifts a fishnet that is laying on the pool floor and rise up via the pistons thus anything that caused the pool alarm to be set off IF "it" fell into the pool "it" will be lifted up.     Hopefully the pistons should be checked by state / consumer advocate authorities to be sure it rises at a certain speed and with a certain weight to save or lower the chances of a child drowning. The careful draining means if the pool alarm triggers draining that a filter assure no part of the baby (i.e. fingers) is caught by the drain opening even if the rising fishnet fence should rise fast enough to prevent anything falling in from even getting close to the drain

The idea came on the fact that in the 1970s my parents took me & sis on a Fla. vacation via Eastern Airlines staying at the ¿Fountain Blue Hotel? and while i was in the ocean a rip tide took me out to a point were the sea floor dropped so much i could not see the sea floor  i held on the beach / higher sea floor's edge while begging to take in water and then  some big fish pushed me up as i was trying to also pull and push myself up.  Eventually i got above the water level and my parents who where ~30 feet away now where smaller than my pinky's nail as i remember my mother having the only bright florescent green top so once i saw that green i held my fingers up to get a size / distance perspective ... long story short i thought why not build a fishnet fence that is secured to a aerodynamic fence that lays low on the sea floor yet when lifeguards think a person is being dragged by a riptide they can remotely trigger that areas ripcatch fence and hopefully the fence catches the person being dragged since the fence and the net are aerodynamically built so it does not allow the force of the water to affect it whether its up or on the beach floor. When remotely triggered the fence is lifted by unlatching wide** buoys secured to beach floor boy mini silos.

problems are costs!!!, making sure no sea floor creatures / fish are affected or build their "homes"  on it and low enough no boat bottom catches onto it.
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** wide instead of tall so they are not hit by passing boats.