It’s a rock.

Squidward appears angry and annoyed, then extends his hand forward in a dismissive gesture. The scene cuts to SpongeBob standing next to a large, dark blue object, smiling widely and waving his hand, before his expression shifts to a smug, closed-eyed grin. The final frame shows SpongeBob's body superimposed onto a close-up of a human penis, with his hand placed on the side. The setting is an underwater environment with sandy ocean floor and coral formations.