How do engines move a boat? How do we travel under the sea? Find out more about ships, submarines and engineering at sea.Do You Know? is a series of levelled non-fiction books featuring video content, project work and critical-thinking activities to motivate and engage young learners. Covering a range of STEM topics from nocturnal animals to climate change, Do You Know? takes an enquiry-based approach, developing children's language, communication and investigation skills.Recommended for children aged 7+, there are four levels progressing from CEFR level Pre-A1 to level A2. Each reader is accompanied by online video content, audio, video and comprehension activities, and suggestions for project work. At Sea, a Level 2 Reader, is A1 in the CEFR framework and supports YLE Movers exams. Short sentences contain a maximum of two clauses, introducing the past tense and some simple adverbs.