Sea Monster - Sea Monster Series, #1

Alicia, driven by her love of the ocean and her curiosity about mysterious sea creatures, organises an expedition. Together with Tom, Lily, Jack and Michael, she sets sail on the Ocean Explorer deep into the Atlantic Ocean. On their journey, they encounter storms, equipment damage, food and water shortages, and strange creatures and mysterious symbols on a mysterious island. Later, they are trapped in a cave by a storm and discover a huge whirlpool.
They decide to venture into the whirlpool and arrive in a mysterious underwater world...