My idea for a pirate would be a College of Eloquence Bard taking a few levels of Warlock. Primarily a caster that specialises in conducting parley either to negotiate terms of surrender or to distract unwitting merchant vessels for the crew to sneak up and surround. A lot of story potential either as the charismatic captain that keeps the rowdy pirates at heel with sweet terms, or a scheming first mate plotting to overthrow his belligerent captain.
Pirate background is great, especially with Fisher's Background Feature: Harvest the Water & proficiency in Vehicles (Water) & Navigator's Tool. I would do a Wood Elf original Beast Master Ranger. Lots of fish (& sharks) & birds. I like Ritual Caster (Druid.) I'd pick up Druidcraft & Shape Water through Druidic Warrior. I love Four Elements Monk & 2 levels into Tempest Cleric with Metamagic: Transmuted Spell to Transmuted Fireball (Fire --> Lightning) or Cone of Cold (cold --> lightning). Shape the Flowing Water would be incredibly useful.
Swashbuckler Rogue aarakocra with the pirate background. He is the feared captain of the ocean. If you wanted to you could add some inspiration from "The Princess Bride" pirate
Zealot Barbarian of Umberlee, who I made a Lizardfolk. Was reflavored as a dude that was cursed in a different way, asked for her help and was turned into a ocean monster as said help. Surprisingly, he was really into being a monster and so yeah he is all about his goddess that did him a solid.
