Humm. Pretty regular holes. Legs for a recently removed ASW deep sea MAD (Magnetic abnormality array)?
Or still buried and recently used docking device for the same. Need to blow some of the gravel away and see what they find. Maybe just rectangular bobbit worms, or maybe they found the entry lock to the secret deep sea hide out of now grown up Tom Swift! (Who was a different color when I was growing up.)
Somebody will do an analysis of the photographs and then we'll know just how 'regular' they are. The photo is taken from an angle that makes it difficult to judge. Even so, it's roughly a straight line which is interesting in itself.