Perhaps you should try some spelling variations:
"synchronised swimming" » "synchronising swimming", "synchronised stemming"
"synchronized swimming" » "synchronized stemming", "synchronizingd swimming"
"synchronism swimming" » "synchronism stemming", "synchronising swimming"
"synchronize swimming" » "synchronize stemming", "synchronizing swimming"

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (((("synchronised swimming") or ("synchronized swimming"))) or ((("synchronism swimming") OR ("synchronize swimming"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("synchronised swimming") OR ("synchronized swimming"))) OR ((("synchronism swimming") OR ("synchronize swimming")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"synchronised swimming\") or (\"synchronized swimming\"))) or (((\"synchronism swimming\") OR (\"synchronize swimming\"))))".
• Removing quotes may allow a broader search: (((( synchronised swimming ) or ( synchronized swimming ))) or ((( synchronism swimming ) OR ( synchronize swimming )))).
• Adding a wildcard symbol may retrieve word variants: (((("synchronised swimming") or ("synchronized swimming"))) or ((("synchronism swimming") OR ("synchronize swimming"))))*.