Just your normal everyday submarine, passing by your canoe very close to shore in what appears to be a lake.
Not even sure if context would help
I got rather curious and Googled it.
https://dc.fandom.com/wiki/Superman's_Pal,_Jimmy_Olsen_Vol_1_68
“The Human Metal-Eater!”: After Jimmy is bitten by a Metal-Eater in the Fortress of Solitude, he gains the power to eat and digest metal for 48 hours.
The crooks use Jimmy Olsen’s Signal Watch to trap Superman and Krypto in a submarine with the kryptonite; but Jimmy saves the day by eating the kryptonite, with a little lead on the side.
It doesn’t help that much, no. He’s gonna eat the whole sub, starting from the periscope…?
Jimmy Olsen loves to munch on something that’s long, hard and full of seamen?
Pica
What does she have to complain? He even got fancy-dressed for this periscope lunch