Underwater Helmets (Alderney 1998)

Souvenir Sheet Underwater Helmets it reflects the thematic directions:

An anniversary is the date on which an event took place or an institution was founded in a previous year, and may also refer to the commemoration or celebration of that event. For example, the first event is the initial occurrence or, if planned, the inaugural of the event. One year later would be the first anniversary of that event. The word was first used for Catholic feasts to commemorate saints. Most countries celebrate national anniversaries, typically called national days. These could be the date of independence of the nation or the adoption of a new constitution or form of government. The important dates in a sitting monarch's reign may also be commemorated, an event often referred to as a "Jubilee".

Water sports or aquatic sports are sports activities conducted on waterbodies and can be categorized according to the degree of immersion by the participants. 

Sport is a form of physical activity or game. Often competitive and organized, sports use, maintain, or improve physical ability and skills. They also provide enjoyment to participants and, in some cases, entertainment to spectators. Many sports exist, with different participant numbers, some are done by a single person with others being done by hundreds. Most sports take place either in teams or competing as individuals. Some sports allow a "tie" or "draw", in which there is no single winner; others provide tie-breaking methods to ensure one winner. A number of contests may be arranged in a tournament format, producing a champion. Many sports leagues make an annual champion by arranging games in a regular sports season, followed in some cases by playoffs.