Marvel Comics © May 1967, AVENGERS #40.  The story is "Suddenly... The Sub-Mariner!". 

Appearing: The Avengers  [Captain America [Steve Rogers]; Goliath [Henry Pym]; Hawkeye [Clint Barton];  Quicksilver [Pietro Maximoff]; Scarlet Witch [Wanda Maximoff]; Wasp [Janet Van  Dyne]]; Hercules; Black Widow [Natasha Romanoff]; Thunderbolt Ross; Namor the  Sub-Mariner; Vashti; Mole Man [Harvey Elder]

Works by; Script Roy Thomas   Pencils Don Heck    Inks George Roussos [as  George Bell]

This book appears (f 65), w/ the expected nics, tics, wear and tear.  Thanks for looking.     8342-1903-65