Lobster Plate - +1 Magic Armor
Bright red and orange, knobby, worn over the torso. This offers exceptional protection the back especially; sneak attacks can only deal normal damage against whoever wears this armor- no critical strikes can hit them. Also, magic or skill-based powers that can remove this armor don't work, unless the wearer is at least halfway submerged in water. This armor is as protective as plate armor, with +1 AC.
Once worn by a paranoid captain who feared a mutiny.
 Ivory Putty Jar
Carved from the base of a great whale's tusk- this smooth container has a well fitting cap to keep out air. Inside, it contains a great few fistfulls of wood colored putty which can be smeared onto wood and breaks in a ship's hull. The putty merges with the boards there, gaining their woodgrain and becoming indistinguishable from the natural wood that once made up whatever it is repairing.
The jar magically regrows the putty inside over time; it only greats a spoonful or so every turn, meaning it will take a long time to recharge. But with this jar, a ship can be repaired much easier and with needing less stops. If a full jar is used during a ship to ship chase or combat, you can recover a ship's hull by 1d6 hit points over an exploration turn of patching the worst leaks and breaks.
 Green Gel Lantern
Silver framed glass egg filled with green goop. The goop is inert unless heated by a flame- the tiny fixture for placing a small candle underneath must be lit for the lantern to function. The lantern is always carried with a thick wool bag that can be thrown over it to cover up its light.
The goop emits a massive amount of ghostly green light- the gel lantern essentially multiples the amount of light given off by a flame by a hundred times over. The green light is enough to act as a beacon to other ships, or to illuminate the entire deck from the poop- use a baseline of 80 feet of bright light. The lantern also grants magical protection- anyone carrying it gains +2 to spell saves against any spell cast on them within the green light.
The gel inside the green gel lantern has a secondary power. If heated, the glowing goop can be consumed by a creature to make them shed light of 10 feet and become immune to all magical spells and take half damage from magical blasts, damage from weapons, and dragon breathe for the next six combat rounds. Every time some of this gel is consumed in this way; reduce its bright-light radius by -5 feet permanently.
 Scarf of Tailwind
It's a long waving red scarf. Whoever wears it can control which way the wind blows; the scarf's tail always majestically waving towards the wearer's new desired direction. The strength of this wind is between a cool breeze and stiff blowing- perfect for sailing, but it cannot beat a storm. It can also quell the wind, causing the scarf to hang down limply.
There is no "cooldown" or curse associated with this magic item. That's probably why some obsessed pirate captain beheads anybody who is wearing a scarf and steal them for his collection- he's trying to find the "one".
 Rock of Rismorses
This rock is shaped like a small step pyramid, but more smooth. It was apparently formed by natural forces, except with a few small ridges of tiny notches curved along its surface. This rock must be owned by a pirate captain who can cast spells; because this rock is actually a spellbook.
The rock has three spells etched into it, requiring a small meditation ritual of about a turn to read & prepare by tracing your finger along.
Gulp of Sand - 1st level Conjuration
Causes a mouthful of sand to "come up" from the mouth of whatever the caster points at. It can be a statue, a person (causing them to cough and wasting an action), an animal (making them spit out anyone they have caught in their jaws), and so on. The amount of sand is enough to fill the mouth of the "mouth", and as such a massive statue or huge creature could eject a massive dune of sand.
Anchor - 2nd level Transmutation
Makes anything in the water burdened as though weighed down by an "anchor". This anchor will adjust for the size and weight of the target, but will be roughly enough to keep it from being blown away by the wind, but not enough to cause it to sink. Things with little buoyancy may be dragged under instead. This anchor weight is invisible, but will always hang from the central bottom point of the floating object, and could be "cut" by a magic sword or another spell.
Any aquatic creature or vessel moves as though heavily encumbered, damaged, or having no wind in its sail. You must be within shouting distance to cast this spell on something.
Cant of Survival - 3rd level Abjuration
This spell is a hymn that effects everyone who can hear it. The caster must chant the words without stopping, and can perform no other actions but casting this spell while it is active. While listening to this song, taking damage that would kill you instead reduces you to 1 Hit Point. Every round somebody should have died, the caster must make a saving throw vs magic to continue the spell, else it stops. Every time the caster succeeds this save; make it +1 harder on the next roll until this casting of the spell ends.
These spells are mostly incidental for this stone to have- it's real value as a magical treasure is that it is a rock that floats! It isn't hollow or anything- it just floats in water, so you won't lose it when it gets thrown off the side of the ship.
 The Everlemon
An eternally bitter, sweet, juicy lemon. You'll find this as a half of a lemon; it never "heals" itself but it doesn't dry out or lose its flavor- it is always exactly as fresh as a ripe lemon sliced down the middle. If you suck on it, protects you from scurvy. You can also juice it once per day to create another "scurvy ration" for somebody else, or store it to make a lemonade base for potions.
The first half is owned by a pirate somewhere- somebody you rob. The second half is being ever-digested in the belly of a kraken somewhere else.
 Godless Finger
Finger of an renowned atheist, thief, war profiteer, and temple-sacker. It is kept in a small box and wrapped in black cloth. The finger never rots, but never bleeds either. If the finger is touched to a holy object, it sizzles and burns, letting you identify items consecrated or blessed with divine power. If the item is demonic, the finger might caress it instead.
Additionally; the finger (index finger of the left hand of a human) can be cleanly stitched to your own hand if you remove the matching finger. The moment you do this, you gain its powers and can identify holy or unholy items. You also gain all of the thief skills of a 3rd level thief, and can use their saves in any category if they are better then yours. If you are already a Rogue/Thief, you treat all of your skills and saves as though you were one level higher. However, you can no longer benefit from divine magic- you cannot be healed and conjured food or water turns to dust in your mouth.
 Ballast from the Bay
Not one magic item, but an uncountable many. The "ballasts" are grains of sand from a yellow beach in some part of the world, long since forgotten and unimportant. These grains of sand obey the words of the owner much like a dog. They hate to be separated and the sand will form into a cloud or slither like a large snake over land to be reunited with their "owner". The sand can rapidly duplicate itself or shrink in number; going from a small dune to a powdery handful in about one turn worth of shrinking or duplicating.
You can also order the sand to "attack" people, which it does mostly be just rushing at them or pouring over them- it has no concept of choking people or sand-blasting their eyes. It can do a maximum of one damage per round, but it could weigh somebody down pretty heavily if it got into their bags. It is terrified of water and will never intentionally sink a ship, and cannot fly over any standing water- even a few droplets make it scared. If told to defend you, it would grant +1 AC vs melee attacks and +3 AC vs ranged attacks or magic blasts, except electricity. Any electrical blast that hits this sand causes it to fall to the ground and wiggle and dune-about in a spasm. This is apparently similar to rubbing a dog's belly, but for sand.
Due to its separation anxiety, and inability to actually help any bloodthirsty pirates who come to posses it, it is usually told to stay on the bottom of the ship and act as a ballast, hence the name. Even so, using it for this purpose is enough to grant a big advantage- any ship with a ballast like this would require no anchor, can turn on a dime, and can quickly lose weight to gain speed faster then crewmen dumping cannonballs or less important crewmen off the sides of the ship. Treat any ship related rolls or checks as +1 and the cargo space of the ship expanded by a few barrels or crew-space worth.
The ballast is animated sand but has a certain level of animal cleverness to it. It treats whoever has recently sat on it the longest as its master. Masters who mistreat it (trying to make it carry them over water, burning it and sending it at enemy ships as an attack, etc.) are likely to find it abandoning them by shoving a few of its grains into the stitching of another person's pants- so eventually they will have "sat" on it the longest.