That shot is definitely composed to try to make the stingray look as large as possible, but the video on the site does show it's pretty large.
Here's a screencap from the video with the diver in closer proximity... looks like 6-7 feet or so when one is watching the video... and it's shot somewhat from above so the relative sizes are easier to judge... the guy said he is 6 feet tall, so he measures 8 feet including his fins.
https://www.wfla.com/news/pinellas-county/video-divers-spot-massive-stingray-in-gulf-off-coast-of-tarpon-springs/1866444412