Sorry, this is another long one...
Since your are staying in U.S. Waters, it does make the equation easier.
Not knowing you or your wife's background with weapons, I'll respond as though there were none.
If it's going to be on the boat a lot, then my first choice is something stainless. Blued steel will show rust spots really quick in a saltwater environment. Shotgun is good or a pistol whichever you are most comfortable with.
My personal choice is a short pump shotgun. There is nothing like the sound of a round being jacked into the chamber!!
I agree with stainless, and the sound of a racked round, will get dang near anyone's attention poste haste!!
I also agree with the "whichever you are most comfortable with" comment.
As for the stainless, not only will it hold up better with less maintenance, but if done right, presents a very formidable presence
I don't yet have a weapon on the boat, but have given this considerable thought. My weapon of choice would be a Mossberg 500 JIC 12 ga shotgun with a pistol grip in MarineCote. The JIC kit (Just In Case) includes a sturdy watertight tube and a multitool.
Mossberg ''Just In Case'' Shotgun Package, Marinecoat, Orange Tube - Impact Guns
I want something easily accessible, easy to operate, reliable and effective. This weapon seems to meet those needs.
The nice thing about a shotgun, is that it offers itself to other uses as well, and the ammunition can be varied easily.
The only issue I have with a pistol grip shotgun, is that "some" people simple can't handle them. I've trained volumes and inevitably, we'd have someone, male or female, that simply didn't have the wrist strength or forearm control to keep the weapon on target after the first round was fired. But again, if you find it fits the bill for you and your wife, then by all mean, a very god weapon for on board defense. Carried one in my patrol car for years, and on various LE boats (mostly full stock versions of the same Mossberg LE weapon) and loved it. Very reliable and simple to maintain.
Another thought is this:
Ruger K-Mini14GBF
Ruger® Mini-14® Autoloading Rifles
I've carried this weapon for years and really like it.
Light weight, compact when folded, and uses standard .223 ammo.
You "could" change the barrel out or use an adapter to fire less expensive .22 cal. ammo as well.
Good:
Light weight
Compact
Stainless
Sling
Flash Suppressor*
Bayonet Lug rolleyes
*
Folding stock*
Bad:
Folding Stock*-The stock when extended, fails to provide a solid feel for the shooter. I guess "wobbly" is the best way to describe it.
I replaced mine with a Choate Pistol Grip Stock many years ago. Mine is the 07-01-12 pictured below.
Mini-14 Stocks
While designed as a full length stock, in case you decide you need to "reach out and touch someone", it's easily and neatly tucked in next to the body when utilizing the pistol grip.
Also, while a polymer, it takes the OEM wood out of the equation. May increase the life or reduce maintenance a bit, who knows?
They also offer this one:
Choate Pistol Grip Folding Rifle Stock Ruger Mini-14 Mini-30 Synthetic
and while I've never used it, it's still an option.
It "appears" that it may have the same deficiencies that my OEM Ruger folder had, but again, I've never tried it. May have to do that.
Here is the Choate official website:
Welcome to Choate Machine and Tool - Your Premier Source for Tactical Stocks and Accessories for Rifles, Shotguns and Submachine Guns
Flash Suppressor*- Could be better that's all.
Bayonet lug*-Worthless for all intents and purposes. If I want to stick someone, I'll use something else.
Always seemed to find a way to get hung up on something!
The bigger question is comfort and space. If the weapon is uncomfortable to shoot or carry...you (or she) won't. If it's too large to easily work around bulkheads or carry up/down ladders, then again, it's no good.
It all depends on how much both of you are willing to train?
You can become very competent with almost anything with enough training. And while anyone can punch holes in paper,
PLEASE, PLEASE, try to find someone, somewhere, that can offer you some
tactical training.
Cover, concealment, light/sound abatement, movement, etc.
Defending your boat is much the same as defending your home, except the floors move....
Sorry, I get pretty intense on this part of the subject....
As for a handgun, I'd consider the largest caliber you can both accurately and comfortably handle while firing multiple rounds for several minutes.
If it's not uncomfortable or intimidating for that time, then a couple of quick rounds isn't going to be a problem.
I would stick with a brand name, performance tested in the marine environment, semi-auto, such as the Sig Sauer, S&W, Glock, and a few others.
While the revolvers are "simple", modern semi-autos, with proper training, ammunition and maintenance, seldom jam, misfire, or experience other failures, and are extremely reliable. Again, most failures tend to be the result of:
1) Poor weapon handling
2) Poor ammunition.
Finally, I would consider using a frangible round that is going to expend all or most of it's energy on impact:
A sequence of photos showing a frangible bullet fracturing when subjected to high velocity strain waves
A frangible bullet is one that is designed to disintegrate into tiny particles upon impact to minimize their penetration for reasons of
range safety, to limit environmental impact, or to limit the danger behind the intended target. Examples are the
Glaser Safety Slug and the
breaching round.
Frangible bullets will disintegrate upon contact with a surface harder than the bullet itself. Frangible bullets are often used by shooters engaging in close quarter combat training to avoid
ricochets; targets are placed on steel backing plates that serve to completely fragment the bullet. Frangible bullets are typically made of non-toxic metals, and are frequently used on "green" ranges and outdoor ranges where lead abatement is a concern.
[2][3]
Frangibility - Wikipedia, the free encyclopedia
Depending on the construction of your vessel, an errant round could pass through a bulkhead, hatchway door or window, endangering a family member or other person on board, or damaging vital gear. And that's if
ALL the shooting is done on board in enclosed quarters.
On deck in the open is a whole other ball of wax.
Hope some of this is of some assistance to you in your search.
(THE PICS ARE BELOW- Guess I'm a bit Tech-Tarded when it comes to putting the pics where I want them!!)
Top- Mini14 Folded- OEM stock
Center- Mini14 Extended OEM Stock
Bottom- Choate Full length polymer stock (mine).
OD