Noun: jump, leap, vault, bound.
Hyppy is a noun that comes from the verb hypätä, which means ”to jump” or ”to leap.” (See hypätä conjugated here.)
Usually hypätä refers to a single jump as opposed to a series of jumps. The related verb hyppiä refers to repeated jumping or hopping. Another related verb, hypellä means ”to jump about.”
Let’s translate rest of the headline, ”Hyppy viileään veteen,” ”A jump into the cool water.”
Viileään is the illative singular form of viileä, an adjective that means ”cool.” The illative case is used when the meaning is ”into” something.
Veteen is the illative singular form of vesi, a noun which means water. Vesi is declined like käsi (”arm”). The stem of vesi is vete even though an ”s” appears in the nominative so be careful when you decline this noun. Click here for a list of other words that are similar.