We at Teezily have a number of cool shirt designs for anyone from Plymouth, with a number of nautical designs and catchy slogans to choose from. Holiday makers do want to remind themselves of where they went on holiday so coming up with the right phrase on a shirt would seem to be a good idea.
It's always a good idea to experiment to see what sells well. A simple "A present from Plymouth" on a shirt may suffice. Look for pastel colours for clothing such as blues or yellows that people might wear on the beach, though having said that some designs do suit a black background. Items associated with holidays such as sun designs or ice creams might work well, or a simple bucket and spade, along with a message. Try several designs and see what works for you.