I entered on the far side of the pond across from spawnwhere the ground slopes into the water, after swimming a while and gathering all collectables i was trying to leave the water (closer to the edge near spawn, where the platform is on the water near the dumpster) i charged from the bottom holding shift+W i believe. i went pretty high and after i let go i realized i wasn't going to fall back down.
Sorry i don't have more specifics but i hope this can help!