What kind of fish(?) is this? North shore Massachusetts

Found this little guy in the rocky intertidal zone in the subtidal while the tide was way out. I romp around there all the time but I’ve never seen one of these guys before! Google said flounder but he doesn’t really look like it to me and he’s small (about palm sized if you can’t tell in the video) but I also don’t know anything about fish I’m more of an algae and shorebirds kind of guy. Let me know!