Spartans were great at fighting on land but bad fighting at sea.
Spartans weren’t the expansionist sort. Their territory, Laconia Territory, was fertile as far as Greek lands go, and allowed them to be self-sufficient so they weren’t too interested in building ships and sailing elsewhere unlike the Athenians. So while Athens had a navy, Spartans were mostly landlubbers, and lack of experience with the ocean made them weak as far as sea power went.
Tune in next week for more about the Spartans!