On 17 June, "Sea Dog" rotated areas with "Spadefish" and "Crevalle" and headed north to hunt along the Hokkaidō coast between Bakkai and Kamui Misaki. Two days later, she sighted three merchantmen moving northward along the coast and attacked, firing two torpedoes at the lead ship and three at the second. The third ship changed course. "Sea Dog" turned back to the previous targets. The first ship, cargo ship "Kokai Maru", was going under, stern first. But, before she could fire again on the second ship, an enemy plane was sighted. "Sea Dog" dived. At , she grounded; backed off, cleared and then headed north. The plane did not attack.