SCHOOLS, GROUPS, PARTIES & CORPORATE schools We provide fun, exciting, and educational outdoor activities for schools. Please call for more information of to book. Groups For social organisations, church groups or family outings, we have a wide range of outdoor activities from which to choose. PARTIES Host your function or party at Herts Young Mariners Base, set in the heart of the River Lee Country Park. Just minutes away from the M25 and Cheshunt Railway Station. Corporate Herts Young Mariners Base offers corporate events, conference facilities and team building activities set in the stunning heart of the idyllic Lee Valley Park.