User blog comment:Mythical zoan fruit enthusiast/For those who want Luffy to have Mera Mera and Gomu Gomu/@comment-195.241.127.96-20130503222528/@comment-3517850-20130503232842

Thats cos water only effects a Df user on contact with themselves....Hence why Luffy is effected when any part of his body is in the water.....Aokiji shot his ice to the water freezing it like a freeze ray.