According to the video description:
These sharks were aggressively feeding on menhaden (moss bunker). The frenzy came within 50 yards of the shoreline. The sharks were probably (according to marine scientists), brown sharks, juvenile blacktip and sandbar tiger sharks. This rare feeding frenzy started about a mile offshore and moved into the surf zone in a matter of minutes.
Here's the video shot by Tom Lynch of AngryFish.tv:
Factual depiction of swimming at the Jersey Shore:
