making a new character and was wondering if it’s weird for an Eldritch Knight to be a pirate 

I don't see why Eldritch Knights couldn't be pirates. Focus on Dex, Con and Int, wear light armour and either wield a rapier, or dual wield scimitars. Wizards of the Coast seem to like linking a storm theme with sailors and the sea so spells with lightning and thunder damage and add in movement spells (misty step/fly etc.) when possible. And that's just the mechanical side. Fighter subclasses tend to be a bit more generic in flavour because so many character archetypes could be Fighters. 

At the end of the day, it's your character so it's only wierd if you think it is. 

Why not?  Why does it feel weird?

Your character, you story.   Do it for that reason alone.

Try and find mariners armour if your DM is looking at having heavy weights sink you.. Those on boats dont want to wear heavy armour for a reason. Dont drown its an unsatisfying end to a character right up there with smoke inhalation and rotgrubs.

Stay safe :)

In MTG, the Ixalan block had a bunch of pirate wizards, so Eldritch Knight has basically been in an official WoTC product (I think).