My players quest reward (gold) has been intercepted by halfling pirates off the coast of similar-to-but-legally-distinct-from Ireland. Any one want to save me some leg work or just want to see their favorite brave and lucky salty sea dog sail again? WARNING: ALL NPC'S MAYBE SUBJECTED TO IDIOCY, VIOLENCE, WRONGFUL DEATH, OR UNWILLING CO-OPTING AT PLAYERS DISCRETION. NAMELESS STAT BLOCKS MAYBE PROMOTED TO NPC WITHOUT RHYME OR REASON.

I'll be stating out my own but if any one would like share I am ready to be one upped.

Take the Bandit and Bandit Captain stat blocks, make them Small, add a 20 foot swimming speed (or don't), and give them the Lucky trait (from Halfling). This should give the good-old pirate-halfling feel without getting too many issues.

There is also the Pirate Captain, from Ghosts of Saltmarsh which plays more into the "leader" role than just being stronger.

The Swashbuckler from Volo's is also something you could use with similar modifications as above.

Forgot about the swashbuckler. Would have been a good one. Ended up using Flare's suggestion adding the brave ability and racial ability modifiers. My players ended up parleying with Captain Bevyn FatRabbit and his roving band after sneaking aboard and quickly subjugating his brother. Negotiations went well with the only death that occurred during the boarding action being promptly revivified. The captain furnished the diamond and they promptly repaid for the loss out of the gold they'd come to retrieve. Our heroes then set off wishing the rather gentlemanly Captain farewell, rowed  for two minutes then turned around when they realized they forgot to check for plot hooks. They and Captain Bevyn bonded over a shared faith in Lathander and a love strong tea. Every so often asking "You sure you're not gonna stab us in the back?"   All in all a rather pleasant experience for my players who have been until this point suffering at the hands of demons, gangsters, gangster demons, and my tendency towards grim-dark story telling.

Thanks for input guys. Appreciate it.

I have one coming for you, just putting the finishing touches on it for you, but here’s the preliminary version. Here she is all buttoned up for you. All that’s missing is her Character details, but that would be spoilers. (Bonus points if you get the Easter eggs.): 

Captain Mary Anne “Cap’n Anney” Rackham

Small humanoid (halfling) , chaotic neutral

Armor Class 19 (Mariners’ Studded Leather Armor)

Hit Points 98 (24d6 + 14)

Speed 30 ft., swim 30 ft.

STR

12 (+1)

DEX

18 (+4)

CON

14 (+2)

INT

15 (+2)

WIS

13 (+1)

CHA

16 (+3)

Saving Throws DEX +8

Skills Acrobatics +12, Athletics +8, Perception +9, Persuasion +7, Sleight of Hand +8, Stealth +8

Condition Immunities Frightened

Senses Passive Perception 19

Languages Common, Elvish, Goblin, Grung, Halfling, Orc, Thieves' Cant, and Goidelic

Challenge 9 (5,000 XP)

 

Proficiency Bonus +4

Luck of the Goidelic (1/Short Rest). Whenever Cap’n Anney Rackham misses with an attack or fails a saving throw or ability check you can reroll the d20 for her, and must use the new result.

Precision Accuracy (1/turn). When Cap'n Anney Rackham hits with a weapon attack she can add 7 (2d6) additional damage to the damage roll.

Sea Legs. The Cap'n has advantage on ability checks and saving throws to resist being knocked prone.

Charismatic Combatant. Cap'n Anney Rackham adds her Charisma modifier to the damage roll for her Crescent Cutlass attacks (included in the attack), her AC (already included), and her Initiative rolls.

Crescent Cutlass. This silver-bladed cutlass glimmers softly with moonlight. While holding this magic weapon, Cap'n Anney Rackham has a +1 bonus to attack and damage rolls made with it (included in the attack), and she gains a +1 bonus to spell attack rolls and the saving throw DCs of her spells (included in the Spellcasting feature). In addition, she can use the cutlass as a spellcasting focus for her spells.
   She can use a bonus action to speak this magic sword's command word, causing the blade to shed moonlight, creating bright light in a 15-foot radius and dim light for an additional 15 feet.

Mariner's Armor. While wearing this armor, Cap'n Anney Rackham has a swimming speed equal to her walking speed. In addition, whenever she starts her turn underwater with 0 hit points, the armor causes her to rise 60 feet toward the surface.

Spellcasting. The Cap'n is a 4th-level spellcaster. Her spellcasting ability is Charisma (spell save DC 16, +8 to hit with spell attacks), she knows the following spells:

Cantrips (at will): friends, lightning lure, mage hand, prestidigitation, thaumaturgy, vicious mockery

1st level (4 slots): burning hands, compelled duel, fog cloud, unseen servant

2nd level (3 slots): augury, misty step

Actions

Multiattack. Cap'n Anney Rackham makes three melee attacks: two with her Crescent Cutlass and one with her Dagger. Or the Cap'n makes two ranged attacks with her daggers.

Crescent Cutlass. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 12 (1d8 + 8) slashing damage.

Dagger. Melee or Ranged Weapon Attack: +8 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 5 (1d4 + 4) piercing damage.

Brace of Pistols (3/Short Rest). Once per turn, whenever Cap'n Anney Rackham can make a melee attack she can replace it with one of the following:
Pistol. Ranged Weapon Attack: +8 to hit, range 30/90 ft., one target. Hit: 9 (1d10 + 4) piercing damage.

Bonus Actions

Lightfooted. Cap'n Anney Rackham can take the Dash or Disengage action as a bonus action on each of her turns.

Spells. -- misty step

Reactions

Parry. The Cap'n adds 4 to her AC against one melee attack that would hit it. To do so, she must see the attacker and be wielding a melee weapon.

Shape Up, Ye Scurvy Dog (3/day). Whenever a friendly creature within 30 feet of Cap'n Anney Rackham that can hear her misses with an attack, she can yell perilous threats to allow that creature to reroll the attack roll.

Legendary Actions

If she is wielding the Crescent Cutlass, Cap'n Anney Rackham can take up to two legendary actions between each of her turns, taking the actions all at once or spreading them over the round. A legendary action can be taken only at the start or end of a turn. The Cap'n has the following legendary action options, some of which expend more than one action when taken:

Casting (Costs 2 Actions). Cap'n Anney Rackham can cast a single cantrip, or misty step if she has an available Spell Slot.

Detect. The Cap'n makes a Wisdom (Perception) check.

Melee Attack. The Cap’n makes one melee attack.

Nice. Good action oriented design. Matt Colville would be proud. I'll keep Cap'n Anney in my back pocket should any more high sea hi-jinks unfold.