SeaGreymon is the eighth Armor form achieved by PrimitiveAgumon. He takes the form of a large turtle with Greymon's head. He has lime green fins. SeaGreymon also has a long lime green tail with blue stripes. The horn on his nose is tilted back in order to swim faster. His shell is dark green around the edge, but a lighter green in the middle. The edge is designed with trapezoidal shapes. The Crest of Reliability appears in the middle of the shell.
After Haku had recovered from the battle with BlackVeggiemon, the DigiDestineds returned to the Digital World to look for the next Digi-Egg. They found it in the middle of a lake on top of the water. AncientGomamon used his Ancient Fishes attack to create a bridge to the Digi-Egg. He swam next to the fish bridge and was pulled underwater. Haku leaped into the water to see what happened. Seconds later, he climbed back onto the bridge and told everyone to run to the Digi-Egg. A WaruSeadramon appeared and was revealed to be guarding it for Volatilemon. AncientGomamon resurfaced in the form of TidalIkkakumon and began to attack WaruSeadramon. He was eventually defeated. PrimitiveAgumon reappears in this form whenever the Digidestineds need to travel by water.
Aquas Blast- shoots a large ball of water from his mouth
Grey Soaker- a unison attack with Sakanamon. Sakanamon uses Pure Water, causing water to swirl up around the opponent. Then SeaGreymon makes the water collapse onto the opponent