The chance of a shoulder dislocation in the water is a nagging worry for the habitual paddler. Have a dangling, flagging limb in a storm while holding a deck line with the other, and alas, there shall be biblical weeping and gnashing of teeth.
So, for a time I have been keen to learn how to reduce with ease a dislocated glenohumeral joint with a palpable, audible, satisfactory clunk. There are many ways and if the procedure is performed incorrectly, there are regretfully, as many risks of causing further injury to nerves, vessels, bones, and so on. There is too the chance of being abjectly prosecuted if the reduction is performed unsuccessfully either by laymen or skilled first aid providers, but in this particular point I am of the opinion that kayakers should regards lawyers with nothing but contempt. However, consider the above as my legal disclaimer.
Generally these reductions are performed by physicians, but in a wilderness setting - e.g. not at home in front of the fireplace - if the victim cannot reach a medical center - that is certainly were one would want then to be - within 30 to 60 minutes, the blood supply is cut off to the limb of which blueness, tingling, numbness or the absence of a pulse in the extremity are clear signs, and a fracture is not suspected, relocating the joint immediately might be the best option, as not only a prompt reduction is beneficial for the joint, the longer a shoulder remains dislocated, the more difficult the eventual reduction.
While kayaking, the dislocation of the glenohumeral joint will usually respond to strong pressure in the arm in the abducted - pulled away from the torso - and externally rotated position. A proverbial example of extreme abduction and external rotation of the arm is a high brace, either not properly performed or with  the right position of elbows hanging underneath the paddle shaft and close to the torso altered by the forceful impact of waves. 
Most commonly, the dislocation would be anterior, that is where the head of the humerus is dislocated forward from the glenoid cavity, the large socket that articulates the joint. So, if such an anterior shoulder dislocation is suspected, a sensible preliminary survey should consider the following:
- Carefully assess the axillary and musculocutaneous nerves because they are the nerves most often injured in this dislocation.
- Clear signs of dislocation are holding the extremity away from the body, unable to bring the arm across the chest, and a shoulder that appears square because of anterior, medial and inferior displacement of the humeral head into a subcoracoid position.
- Both restriction of motion through the normal range of the joint and and obvious deformity in comparison with the uninvolved side are signs of a dislocation.
- There is not crepitus unless there is an associated fracture.
- A symptom of axillary nerve injury is a loss of sensation over the mid-deltoid region.
Once you have determined that the shoulder is dislocated, you may want to attempt reduction. There are a number of methods of reduction for an anterior shoulder dislocation. A recent technique suggested by Paul Auerbach, M.D., is the Milch technique which requires to have the victim sit, stand, or lie flat on the back, and then slowly reach, using the hand of their dislocated shoulder, behind their head and try to touch the opposite shoulder. Somewhere on this very slow, steady reaching, as the arm moves upward the humerus head will rotate in place and the shoulder will align itself and pop back into the glenoid. A good way to describe the positioning is to imitate the wind up motion of a baseball pitcher before a pitch using the affecting side. Have the patient take their time and slowly reach upward and backwards as if they were going to pitch a baseball. The movement of this maneuver should be slow, allowing for rest when needed, and it can be done by the victim itself or with the assistance of a rescuer. If you are assisting, cup the elbow of the injured limb, giving it support as you guide the arm through the maneuver. Other hand can be placed on the shoulder to apply support to the joint as it goes through the motion.
What are the advantages of the Milch technique? Clinical studies point several specific reasons:
• Compared with other maneuvers to reduce shoulders, this one seems to be the least painful.
• Once the arm has been brought into complete abduction in the overhead position, all cross stresses exerted by all the muscles involved are eliminated as of all the positions which the humerus may assume, the overhead position is the only one in which all the muscles around the shoulder girdle run in the same general direction.
• Some medical providers are confident that if the technique is done correctly and slowly, then the patient does not even need pain medication to relax muscle spasms.
• It is easily described and easy to remember. It suffices to think of a baseball pitcher.
• It can be performed as a self rescue.
• The tendency to further stretch nerves and vessels is obviated.
• Adding  external rotation of the arm the head of the humerus presents its thinnest profile to the glenoid and tilts the greater tuberosity backwards, thus allowing the head to slide more easily back into appropriate anatomical position, as the glenoid is broader below than above and its vertical diameter is the longest.
Videos with different reduction methods and a modification of the Milch Technique shot by Elisa M Aponte, MD, a resident physician in the Department of Emergency Medicine, New York University Bellevue Hospital Center are available here.