I don't think this should be an either or arguement: I would carry both a series drogue and a sea anchor. Their use is entirely different. Also a boat designed for offshore voyaging should be built so that a boarding sea aft will not compromise the integrity of the vessel. If you look at Passagemaker, the aft flush deck has almost as much freeboard as the bow. There are no doors or openings leading to the aft deck--they are on the sides of the pilot house. George Buehler designs minimize the risks to aft boarding seas in similar fashion. As Scott points out, in contrast, most of the current commercially built voyagers have cockpits aft, with transom doors, large windows aft and a door going to the cockpit (the better boats use a quality door which can be dogged securely shut). If the cockpit is filled with water, there is a change of handling characteristics and the possibility of further damage to the aft cabin structure. A sea anchor is is deployed from the bow to minimize sternway drift--a series drogue is deployed to keep the stern to the seas as the boat has way on--either from the drift of windage, or with small amounts of power. As Mike pointed out there are huge forces on a boat in severe storm seas if it is riding to a sea anchor. I don't know if a sea anchor or drogue would have saved Sir Wiston Churchill in the Sydney to Hobart race, because she had a sprung plank and was an old and tired wooden boat which was picked up by a wave and thrown so she landed on her side. One might argue that if a drogue had been deployed the boat might not have been sideways--but a racing crew would most likely not deployed a drogue (see the inquest: http://www.equipped.com/sydney-hobart/Vol%2005%20Docs/STANLEY%20John%20Micha el%201.PDF (also good read on the life rafts in a storm if you read the entire inquest) I am not sure how to equate fluild dynamics in the human circulation--an area where I have considerable expertise in some of my cardiac research-- and storm seas--an area where I have experienced the severe conditions of sustained winds of over 65 knots with a fetch of thousands of miles. The only valid test is "does it work?" There a number of testimonies about the use of drag devices. There are several other texts which should be reviewd by the passagemaker: Van Dorn' "Oceanography and Seamanship", Earl Hinz "Heavy Weather Tactics using Sea Anchors and Drogues". and Victor Shane's " Drag Device Data Base, " 4th edition. The latter has over 120 actual cases of use of various drag devices. (but like Jordan, he sells a product) Steve Dashew says it well: " The best thing you can do to protect yourself and your floating home in stormy offshore conditions is deploy either a sea anchor or a series drogue, go inside, batten down the hatches, and keep the best radar and radio watch possible while you stay dry and get some rest. These devices allow you to park in relative safety, no steering required. Not all sailboats have the structural integrity at the transom or cockpit configuration to use a series drogue, but if you do, this may be the ultimate survival storm device - orienting stern-to the seas, cushioned by the long, weighted rode of multiple cones that pull the transom up through the white water of breaking wave crests as the swell rolls under the boat. Sea anchors are large underwater parachutes deployed from the bow. These provide more resistance to the seas than series drogues, with more potential for violent snatching, and a slower drift speed, an advantage compared to the series drogue if sea room is limited. We carry both a sea anchor and a series drogue, both ready to go in case of deteriorating conditions, and the attitude that we'll deploy one or the other as early as possible in the development of the storm." See:http://www.setsail.com/ A great site to explore. Go the the Dashew offshore and click on the FPB series--and see what they are doing on the new power boat. Steve Dashew's book on heavy weather sailing is also a worth while read--although it pretains mostly to sailboats, the tactics are similar. One has to substitute power boat for sailboat--but the same applies and the boat must be seaworthy. The series drogue keeps the stern to the seas, and prevents both pitchpoling and the boat getting sideways to a wave. A sail boat can be set up with the center of effort way foreward (small storm jib set)--but a power boat will often have the center of effort (windage) amidships or aft, and be more subject to turn sideways to the wind. Also most sailboats have much larger rudders which are more effective in steering in heavy seas. I found that the auto pilot would keep the boat at about 150 degrees (Quatrering with the seas) to the wave set in 30 to 40 foot seas and 60+ knot winds, with a small storm staysail foreward and the engine ticking over to give a constant flow of water over the rudder to allow steerage, even in turbulant water. When a wave broke on the aft deck, there was a companion way opening on the stb side aft on the pilot house (about 15 feet from the stern), about 50 gallons of water cascaded down the companionway. If I had fitted storm slides inside of the doors or had sealing doors (those doors present had ventillation slats about 4" x 12" in each door) the water intrusion would have been prevented. With the boat at 150 degrees to the wave train, she would surf down the wave, but not stray much from the set course. A series drogue would have kept the stern square to the waves. So it is both boat design, tactics and equiptment which may determine a boat's survival in extreme storm conditions. Bob Austin