BACKGROUND OF THE INVENTION 
     Passenger ships are equipped with lifeboats and life rafts. The lifeboats and life rafts are intended to be emergency boats for carrying the persons on the passenger ship should it have catastrophic failure. While the number of spaces in the lifeboats and life rafts is sufficient for the number of persons on the passenger ship, there is the organizational problem of getting the people to the lifeboats and life rafts. There are lifeboat drills, and the passengers are instructed as to what actions to take should an emergency occur. The passengers are instructed to don their flotation devices in the form of life jackets and report to a specific lifeboat station. Such lifeboat drills are usually successful. However, should an actual emergency occur, it is quite possible that some of the lifeboats and life rafts are unuseable. It is also possible that, in the confusion of the emergency event, the distribution of the persons to the lifeboats and life rafts may not be optimum, and some may be overloaded. 
     A life jacket may hold up a person in the water, but the person must escape from the sinking ship in order to avoid being pulled down in the turbulent waters resulting from the sinking of the ship. Thus, a life jacket is not enough since a certain amount of strength and knowledge about swimming is required in order to save oneself. 
     SUMMARY OF THE INVENTION 
     In order to aid in the understanding of this invention, it can be stated in essentially summary form that it is directed to a flotation device which has thereon propulsion structure which can be hand-powered by the user. The propulsion structure preferably includes two cranks connected to separate propellers so that cranking with both hands causes propulsion and cranking with one hand more than the other causes steering. In this way, a user can employ the flotation device to support himself in the water and to propel himself in and with the water. 
     It is thus a purpose and advantage of this invention to provide a flotation device which can be attached to a person to permit him to float in the water and without danger of losing the flotation device, together with a propulsion structure on the flotation device to permit him to move through the water and steer his way through the water. 
     It is another purpose and advantage of this invention to provide a thermal suit which provides the user with some insulation from the chilling properties of the water together with a flotation device which can be attached to the thermal suit. 
     It is another purpose and advantage of this invention to provide a flotation device which is propelled by propellers which are individually powered by the two hands. 
     The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following description, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a survival suit suitable for attachment to a hand-operated propulsion structure in accordance with this invention. 
         FIG. 2  is a front view of a survival suit with a hand-operated propulsion structure attached thereto, in accordance with this invention. 
         FIG. 3  is an isometric view of the hand-operated propulsion and flotation structure, with parts in the exploded position. 
         FIG. 4  is a section taken generally along line  4 - 4  of  FIG. 2 . 
         FIG. 5  is a longitudinal section taken generally along the line  5 - 5  of  FIG. 4 . 
         FIG. 6  is an isometric view of a similar structure, showing cushioning on the flotation device. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIGS. 1 and 2  show survival suit  10  as being worn by a man  12 , with only his head shown in dashed lines. The survival suit has a front closure  14  which permits the survival suit to be donned and doffed. The survival suit  10  is shown as being sleeveless and without leg covering. It may have both of those items. The survival suit is in the nature of an insulated suit which will protect the user against the cold of the water. It is structured so as to perform this function in the environmental conditions in which it will be used. The survival suit has four connectors  16 ,  18 ,  20  and  22  which are used for detachable attachment to the flotation device  24 . Flotation device  24  has a hollow hull  34  having a top surface  36  which can be comfortably engaged by the man against his chest. Connectors  26 ,  28 ,  30  and  32 , respectively, on the hull are disengageably connected with the connectors  16 ,  18 ,  20  and  22 , respectively. The near side connectors are shown attached in  FIG. 5 . 
     The upper platform of hull  34  is generally horizontal and rectangular, as seen in cross-section in  FIG. 4 . It carries downwardly directed keels  38 ,  40  and  42 , which keels define tunnels  44  and  46  therebetween. The tunnels create a space for the machinery and help protect the propellers against damage. The top surface of the hull  34  is contoured so that it provides comfort. It carries chin cushion  35  to help hold the man&#39;s head out of water. The hull is the primary flotation device. It also carries the propulsion structure. The survival suit may also have flotation characteristics, but its primary purpose is to provide thermal insulation to the body. It may be a wet suit or a dry suit. When the survival suit is a dry suit, flotation volume is usually provided on the interior. The survival suit may provide partial or full flotation characteristics. A full dry suit is sufficiently large to utilize a standard life vest therein. The survival suit is primarily designed to be worn on the naked body. However, if provided for use during an emergency, the survival suit has to be oversized so it can be worn over normal clothing. It is the combination of the survival suit together with the primary flotation device—the hull—which provides the three elements necessary to aid in survival: flotation, insulation and propulsion. 
     Crankshaft  48  has a crank handle  50  thereon. The crank handle is freely rotative and has a soft grip thereon for ease of grasp. Crankshaft  48  extends through a bearing in keel  38 , see  FIG. 4 . Interiorly of the keel, it carries face gear  52 . Pinion  54  is in gear tooth engagement with the face gear  52 . Pinion  54  is mounted on propeller shaft  56  (see  FIG. 5 ). Since the pinion is smaller than the face gear and has fewer teeth on the pitch diameter than the face gear, one rotation of the face gear causes a plurality of rotations of the propeller shaft. Propeller  58  is mounted on the propeller shaft and rotates therewith. Rotation of the propeller causes forward thrust to move the hull in the forward direction toward the viewer in  FIG. 4  and to the right of  FIG. 5 . The structure from the crank to the propeller thus described is in the right tunnel  44 . A mirror image structure is also provided in the left tunnel  46 . Crankshaft  60  carries crank handle  62 . The crankshaft  60  extends through the keel  42  and carries face gear  64  in tunnel  46 . Pinion  66  is in gear-tooth engagement with the face gear  64 . Pinion  66  is mounted on propeller shaft  68 . Propeller  70  is mounted on the rear of the propeller shaft  68 . Turning of crankshaft  60  causes rotation of the propeller  70 . 
     It can be seen that rotation of the right-hand crankshaft  48  causes the right propeller to turn. Rotation of the left crankshaft  60  causes the left propeller  70  to turn. The propeller shafts are mounted on struts in the tunnels underneath the hull  34  and are laterally offset from each other. Thus, cranking of one crank harder than the other causes more thrust on that side to cause the apparatus to steer. 
     In case of emergency, the man puts on his survival suit and then straps on his propulsion structure. When he goes into the water, he can separately crank the propellers. An additional advantage occurs for the case where one arm is injured or weaker than the other. The man can still get propulsive effort, but has more difficulty in choosing his direction of travel. 
     The hull  72 , shown in  FIG. 6 , is the same as the hull  34  including its keels, cranks, gears and propellers. It also has the same connectors  26  and  34 . The cushion  74  overlays the hull  72  and provides both cushioning and flotation. It is thus an addition to or instead of the chin cushion  35 . The cushion  74  is of rectangular construction and has upper and lower fabric layers which are joined together at the selvedge edge  76 . These fabric layers of the cushion need not be waterproof. Within the cushion between the top and bottom layers thereof is a layer of closed cell synthetic foam material which provides both the cushioning and the flotation. The edges of the cushion have connectors at the side edges and the crotch, which coincide with corresponding connectors in the survival suit. Only some of these connecters are shown in  FIG. 1 , but additional connectors would be provided on the survival suit to correspond to the connectors on the cushion. This flotation device with hand-operated propulsion structure also permits the user to be supported in the water and to provide for his own propulsion. 
     This invention has been described in its presently contemplated best modes and it is clear that it is susceptible to numerous modifications, modes and embodiments within the ability of those skilled in the art and without the exercise of the inventive faculty. Accordingly, the scope of this invention is defined by the scope of the following claims.
The flotation device with hand-operated propulsion structure comprises a hull with right and left hand cranks. The hand cranks are each connected to rotate its own propeller so that steering is achieved by different cranking and propulsion is achieved by cranking on both manual cranks. In addition to the hull with cranks and propellers, a survival suit is provided with corresponding attachment for the securement of flotation and propulsion devices thereto.