Beach Boss Chests are items that can be obtained by defeating the King Krab boss that can appear at the Beach. It, like other Main Hub boss chests, can drop gems, crate keys, hoverboards and a pet. Beach Boss Chests cannot be burned at the Incinerator in the Junkyard.
As of v1.103.0, this item can be converted by the Main Hub Gumball Machine into Gum. The exchange rate is 1:1.