You have to take into account that you should prepare just the necessary luggage to have life mostly on board, as a real sailor. First, choose a soft bag that you can fold and easily stow (trolleys and rigid suitcases are banned). It is important to check the climate condition on destination to take only the necessary things with you! For example, if you are going to travel during summer to Caribbean or Mediterranean you should only need a good number of bathing suits, t-shirts and shorts, underwear, a pair of long trousers and a sweatshirt or a light jacket weatherproof to use in the evening or in case of eventually rain. Flip-flops or beach shoes for walking on the beach and a pair of sneakers with white soles to move around safely on board (heels and shoes with hard soles banned).
And obviously, don't forget a cap, sunglasses, beach towel and suitable sun protection and antimosquito spray. The boat and the sunlight’s reflection on the water give a very intense tan. Finally, take with you your specific medicine if you suffer from some chronic disease as well as antihistamines, antinausea and paracetamol.
