With Sweep into the Sea, can you push Invaders into the Ocean on a board where Ocean's Hungry Grasp has presence?

Yes, absolutely.

If the Invaders are in a Coastal land, with Sweep into the Sea you can choose to either push them into the nearest Ocean (which is right there) or destroy them; with Ocean's Hungry Grasp in play, it will usually be better to push and Drown them.