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

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