Sea Cadets is the UK's largest maritime youth charity.If you are between 10 and 12 you can join as a Junior, 12 to 18 as a Sea Cadets and 13 to 18 as a Royal Marines Cadet and join 14,000 other Sea Cadets across the UK.As a Sea Cadet you can go to sea, learn to sail and do adventure training, all on a naval theme, plus get extra qualifications to give you a head start in life.TS Formidable is one of two units in NI with Royal Marines Cadets.