Benefits of Amphibious Items?

Question

Okay, this is another question related to my drop mechanic, a question similar to Wingjaw Steel: Superior Armor and Weaponry? in that it concerns a monster's effect on items.

You see, when a monster is killed, its magic infuses the item used to kill it. Also, the life force released upon death interacts with ambient magic and objects in or around the monster to create Drops, which range from body parts to coins and adventurer gear (armor, weapons, random knickknacks). This is relevant because a Mage can "craft" parts of a monster into an item and activate its dormant magic to create an enchanted item.

The monster this question concerns is a Snapper, which has four webbed feet (no legs) and a box-like body (think boxfish) that tapers to a wedge-like point in the front, which is split in two by a large, horizontal mouth with prominent fangs. Basically, a Snapper is all jaws and stomach, and their behavior reflects that. Unfortunately, Snappers spawn anywhere with stagnant water large enough to hold them, as well as in wells left alone too long, puddles, and tide pools.

However, Snappers are dang useful for one thing. When they are killed, their magic becomes an Amphibious enchantment on the item used. The Amphibious enchantment prevents the destructive effects of water (or saltwater) on objects, so you can use an Amphibious kleenex underwater. Additionally, Amphibious items have the same drag underwater as they do in air. This makes metal weapons much more viable for marine usage.

EDIT: As stated above, the Amphibious enchantment gives an object the same drag in water as it has in air, but Amphibious items also retain or exhibit buoyancy. In other words, being in water is like being in a wind tunnel for humans; one doesn't usually float in air, but with a strong enough updraft it is possible!

However, I wonder how useful this will actually be, so my question is: How Beneficial Would The Amphibious Enchantment Be On General Items?

Thank you for your input and feedback, I really appreciate it! (In other words, if you see a problem or need more information, let me know so I can add it!) If you decide to VTC or downvote, please give me an explanation so I can improve this question and make better ones in the future.

Final Notice: For those who answered this question, you have my sincere thanks. Since your answers were all equally helpful, I found I couldn't accept just one, and I hope you understand that.

Answer 1

Some benefit, but lots of unexpected drawbacks.

Everything "Amphibious" will immediately sink to the bottom of the water - because its behaving underwater as it does in air, and when I let go of something in air, it falls to the ground, which in this case is the seafloor.

A "non-amphibious" human swimming in the ocean is using an amphibious sword to slay someone - if in the critical part of the battle he drops the sword, it will fall to the sea floor (average depth on Earth of about 4km) at hundreds of km per hour, either shattering into pieces or embedding meters in sand depending on exact topology.

I hope the adventures in their quest to retrieve the magical amphibious sword of destiny from the seafloor have spells capable of simulating the correct gas densities and mixture ratios required to survive at each increment of their journey. (Sufficiently advanced magic should be indistinguishable from technology, after all). A similar problem comes up if you have an "Amphibious car" - either it immediately fills with water, or more air needs to be magically generated (and the gas ratios changed) as it drives down the hill of the continental slope.

Also note that an "amphibious boat" will not float - it will behave as if the water is air. An "Amphibious bucket" may not be able to hold water (as if it's not interacting with the water normally how does it collect it?). I may be able to use amphibious matches on amphibious timber to start a fire, but the fire is immediately doused by the water, or otherwise smoothers when oxygen can't reach it.

Some things require interactions with moisture to function: Ie "Amphibious superglue" will never set (as it needs to get some moisture in - usually humidity is enough). An "Amphibious desalination machine" or even "Amphibious reverse osmosis water filter" will function as if they're empty. A "Amphibious canteen" may never be able to filled up.

Answer 2

Infinite energy

"X has the same drag in water as it has in air" = water has the same drag as air on X.

Enchant a water screw and have it drop water on the same water mill that moves it. You get a perpetual motion machine with a surplus of energy. I would put a troll physics diagram here but last time I did I got a warning.

Once you have infinite energy through magic, D&D (or Disenchantment) like worlds are possible. Building pyramids becomes a matter of patience. You could drain seas and turn deserts into lakes with enough time and planning. Happy world building!

Answer 3

Boats. Per @Ash, an "amphibious" boat won't float. But if the amphibious boat has a small hole in the hull, and a normal boat floats inside the amphibious boat, and the amphibious boat is held up by the normal boat, then it will be held level with the water line, and it will move through the water without resistance, and the normal boat will sit in the midst of its little lake of co-moving water without needing to fight any resistance at all. So the only requirement is a double hull. Then the normal boat can have a normal screw protruding out the holey hull, which interacts with the water normally to provide propulsion unopposed by drag.

Nets. The "amphibious" net moves through the water with the greatest of ease. Dragged behind the boat above at a hundred knots or so it should be very effective (you may have to slow down a little to make sure you don't lose your net to a dolphin or press fish fillets through the holes).

Matches. Nobody expects a frogman (or frog-man) with a magic match that works exactly the same in water as it would in air. If you can wipe your nose with a magicked tissue underwater, you should be able to do this. The flame produced is made from the material in the match, so it contains the same "amphibious" component, so I suppose it could engulf the victim boat from underneath. Trippy.

Seaplanes. A gift fit for a Kennedy, these delightful aeroplanes don't need to stop at altitude zero. Yes, yes, @Ash reminds there's no air to power the engine, which is why you start it with a magic match.

Watering cans. Have you ever dropped a match on the sea bed and accidentally caught the weeds and debris on fire? Obviously you need an "amphibious" fire extinguisher to put it out, but it might be simpler to have an amphibious watering can. Fill it up with water on the surface, and it should still work the same way below water, right? So pour your water out of the can and it will splash down and put out the fire. Keep one on your boat in case there are frog-men about. You might need one (filled with fresh water, of course!) to water the "amphibious" corn kernels that you're farming on the bottom of the ocean; I'm not sure.