I bought one of these today for my girls and they are so reasonable and good for the beach:
direct.asda.com/george/kid-s-clothing/older-girls/dresses/printed-towelling-dress/G EM35263,default,pd.html
And a fab costume too (which is a Boden like print!):
direct.asda.com/george/kid-s-clothing/younger-girls/swimwear/flower-frill-swimsui t/GEM35559,default,pd.html