Dear Sir: (Punctuation!)
I would like to apply for the position of lifeguards (plural?) assistant which I saw advertised in the New York Times newspaper.
I am 18 years old. At present I am a student at University of Buenos Aires. I am a good swimmer because I had been training (tense) a lot of (informal!) years for swimming competitions. For the last two years I have been studying at Santa Teresa School. When I was a child I used to dream being a beach lifeguard assistant.
(extra information!!)
I feel I would be suitable for the job since I had worked (tense) as a lifeguard at Miami Beach and also as a (grammar) instructor for 3 years at a Swimming Club in London.
When I was a high school student, I participated in an international swimming competition, which I won, therefore I consider myself TO BE a good swimmer. I am also a very enthusiastic and responsible employee, apart from an extrovert person.
I hope you will consider my application. I would be grateful to attend an interview during the next week if it is possible. I look forward to hearing from you in the near future.
Franco Gravante