Dear Sara,
I have spearfished all my life so a few tips on gun "etiquette".
Actually, no loaded gun should be up on deck BUT things can happen. An emergency with a diver in the water may force you to return to the boat and quickly get out of the water--gun in hand.
So what do you do? If it's a "band" gun--with elastics, you have several choices. First, don't point it over the side of a boat and fire it straight down--you may hit someone under water. If you are not familiar with loading this type of gun, you will have no appreciation of the power of some elastics. If you cannot discharge the gun safely, horizontally in the water with all divers accounted for, then store the gun vertically, point down--if it discharges, the body of the gun will move upwards with less speed than the spear shaft (if aimed upwards). Also, the spear will not be suddenly yanked back toward the boat when the line pulls tight. Make sure the safety is on. If you can "store" it horizontally on the dive platform, pointed at right angles to any ladders, you can achieve some safety--divers coming around the platform to the ladder will be at some risk. Back wash over the platform may prevent this method or result in a discharge.
If the gun is pneumatic, DO NOT DISCHARGE THE GUN ABOVE WATER--IT WILL BLOW THE END OFF THE GUN AND YOU MAY BE INJURED. These guns REQUIRE water to be in the barrel when discharged, this prevents the piston and spear from travelling too fast and literally knocking the end off the gun. The spear from a pneumatic gun can travel underwater at over 250 mph. Band guns have slower shaft speeds.
A submerged, horizontal discharge can be done--all divers whereabouts have been ascertained. It the gun has a power selector switch, move it forward to the low power setting, then discharge. If you know how to set the power selector switch (if it exists) you can safely discharge the gun by placing the spear point in a corner of the boat and pressing all your weight onto the back of the gun. You will feel the spear go into the gun...depressing the trigger then will release the spear and your body weight is sufficient to control the spear...simply let the spear out a little at a time. DO NOT DO THIS ON FULL POWER--you may not be able to control the spear. It can bend into a U and throw you back. If you are unsure, then store it spear tip down, in a verticle position, safety on. You can put the spear into the gunnel rod holder hole in the side of the boat.
Of course, the best way to bring the guns up is unloaded. I use a pneumatic, so I always discharge on low power before boarding. Band guns can be "unloaded" but it takes strength and anticipation of how strong the elastic is...if you are not sure, pull the trigger underwater. It would be good if you asked how a particular gun works, just in case you have to handle it.
Now for broken fingers. My first aid kit has aluminum finger splints. You can buy them at most good pharmacies. They can be taped to the injured finger. Splinting to an ajacent finger is also possible as mentioned before but there will be more movement. Elevate the hand and don't dive again. Ice it--but it will hurt.
There is no over the counter medication strong enough for a broken finger. The Lorcet, if tolerated is good. The anti-inflammatories you mentioned, even at prescription strength, work slowly and while they may eventually be enough, they won't work fast enough.
No diving on Lorcet. This is a potent narcotic and in some people it will cause nausea. Do not use it in cases of DCS--it messes up the clinical findings of the docs doing the evaluation.
Speaking of first aid kits, don't expect the dive boat to have what you need. Bring your own and stock it according to your experience. Remember, if you are traveling, any prescriptions for things like Lorcet must have your name on it and have a reasonable quantity. You don't want to be accused of smuggling.
I'm sure I left something out...sorry. I'm also sure that fault can be found with any "suggestions" for storage or discharge of loaded spearguns on board a boat. This situation does occur on occasion and it has to be dealt with safely. If you are not sure, just store it vertically, safety on--if it discharges, it's moving away from people on the boat or in the water.
Hope this helps,
Larry Stein