We've lived in tick country for 16 years and knock on wood no Lyme. Lady with Labs we train with has had it in all her dogs. Our vet believes in Lyme vaccination and her vet does not! We start them as pups and then yearly. Have used Vectra and Frontline Plus. Both are waterproof to some extent. It is wise to put them on and keep dog dry for 24-48 hours before swimming first time. I understand price of Doxycline has gone up quite a bit.