What did the kelp say to the current?

This joke rides the tide of clever wordplay, specifically a delightful pun. The humor hinges on the dual meaning of "wave" and the literal interpretation of the idiom "go with the flow." When kelp tells the current to "just go with the flow," it's not only giving sage advice about adapting to circumstances, but also playfully acknowledging the current's actual movement. The punchline then doubles down, with the kelp promising to "wave from here," referring both to the friendly gesture of waving goodbye and the literal, undulating motion of kelp in the water (Review).

Kelp itself is fascinating, a large brown algae that forms dense underwater forests in cooler, nutrient-rich waters. Unlike land plants, it doesn't have true roots, but rather a holdfast that anchors it to the ocean floor. Its long, flexible fronds are constantly moved by the very ocean currents the joke mentions, creating a mesmerizing, swaying dance that looks very much like it's "waving." This natural movement provides the perfect backdrop for the joke's watery wit, giving a familiar marine scene a humorous twist.