This cartoon-style children's adventure features some well-known Muppet characters from the Sesame Street television series, notably the furry red monster, Elmo.
When he visits Oscar the Grouch in his underwater research lab and expresses interest in Oscar's plan to collect junk from the ocean, Elmo is recruited to pilot a submarine and collect all the junk he can. The category of junk changes from game to game - coins, rings, etc.
The player moves the mouse to guide Elmo and his yellow submarine through the depths of the ocean; one click stops the vehicle and another click changes the cursor to Elmo's underwater tool, which is a mini-sub with a hand, flashlight, or microphone attached. Clicking the icons at the bottom of the screen changes the tool currently in use. Other icons show what kind of junk Oscar wants and how much of it has been collected so far; Oscar's garbage can, which brings the player back to the lab, and an exit door.
As the player explores under the sea, he will come across creatures and objects to interact with and Muppet characters with mini-games to play:
Rosita and the Clan of the Cave Pairs - use the flashlight tool to find matching partners for some ocean animals;
Telly and the Lost City of Atlantis - replace fallen shapes on the Atlantean walls to bring murals to life;
Miss Octopus' Garden - plant seeds to finish patterns of vegetables;
Zoe and the Shallows - listen and find the swimmer making the sound Zoe asks for so she can tell who's swim time is up;
Grover and the Sunken Shipwreck - push a lever to create a path in the right direction for Clammie to reach a treasure.
When the player returns to the undersea lab, Oscar tallies up the collected junk, and if it is enough, he will use it to create a surprise.
Elmo's Deep Sea Adventure provides practice in the preschool skills of pattern recognition, problem solving, shape and color matching, audio discrimination and counting.