Underwater hockey and underwater rugby were both invented in Europe, the former in 1954 in England, where it was first known as "octopush", and the latter in 1961 in Germany, where it is called "Unterwasserrugby". Both sports have interesting and informative Wikipedia articles at
Underwater hockey - Wikipedia, the free encyclopedia
Underwater rugby - Wikipedia, the free encyclopedia
respectively.
The fins traditionally worn by underwater hockey players have been Technisub Ala all-rubber closed-toe full-foots:
Sadly, they're no longer in production. They're excellent fins and because they're made from rubber, their blades are less likely to cause injury to fellow-players than their plastic equivalents in what is a contact sport in the confined area of a swimming pool. In New Zealand, some underwater hockey players substitute for Technisub Alas Japanese-made all-rubber full-foot Gull Hard Mew fins:
I've got a pair and they are excellent fins too, but sadly they're not distributed by the manufacturer in Europe or America.
Underwater hockey fins were traditionally worn with colourful rubber fin grips, which fit over the heel, ankle and instep to secure fins during play:
The French Underwater Hockey Federation used to sell South African-made ones made in red or yellow as well as black, but only black is now available outside the Far East.