the.com/sea anchor

means A cone-shaped drogue deployed underwater from the bow to hold a vessel's heading into waves and slow its drift in a storm.

from A plain compound of 'sea' plus 'anchor' — honest, functional nautical naming rather than borrowed myth. It emerged as sailors needed a word for a device that behaves like an anchor but grips water instead of seabed, since in deep ocean there's no bottom to hook onto. The parachute comparison is modern and apt, but the term itself is just old maritime English doing what it does best: naming a tool by what it does and where it works.