Bill Belichick has himself a catch in Jordon Hudson, literally ... 'cause the immortal head coach and his 24-year-old girlfriend debuted a couples-themed costume this Halloween! Jordon and Bill posed for a few sandy snaps in the Atlantic -- with BB dressed up as a fisherman, and Hudson as a mermaid. BB and JH are both sporting huge smiles ... and it's crystal clear they're enjoying the spooky day together! Of course, TMZ Sports broke the story ... Belichick and Hudson met on a flight in 2021, where they became fast friends. At the time, the then-Patriots head coach wasn't single -- he was with his longtime girlfriend Linda Holliday (speaking of, LH dressed up as Uma Thurman's character from "Kill Bill" ????). However, Linda and Bill, after years of dating, split in 2022. After carrying on a friendship through 2023, Jordon and Bill got romantic ... and, it's been happily ever after since. In fact, earlier in the week, Jordon wore one of her man's old NY Giants shirts ... choosing to dress up as coach at another Halloween event. Looking back at the past few decades, Belichick didn't have too much time for Halloween ... as it falls smack dab in the middle of the NFL season. But, no (coaching) job, no problem, for Bill, who's happy to be gone fishin'! And ya thought Bill didn't have a sense of humor ...