At least 150 vessels, including blockade runners, are listed as having been in the African theatres of war: on the lakes and oceans. The spreadsheet contains details of the nationality, captain, capacity in which the vessel served, and references where known.
An invaluable starting place for researching British ships involved in the First World War, including in Africa, is Naval History which covers the Royal Navy (support vessels).
Crew names, where known, are on the relevant theatre of war name index spreadsheet which can be downloaded.
In the British forces, men were either in the Royal Navy or Royal Naval Volunteer Regiment. Some served in the Royal Naval Air Service.
Major encounters included:
Action on Lake Nyasa (1914)
Konigsberg in the Rufigi Delta (1915)
The Lake Tanganyika Expedition (1915-1917)