After the release of Free! Take your Marks movie, a teaser visual was shown on its post credit. The anime will air on the Summer of 2018 so it may be on July-September. The date is uncertain but will make a further announcement about the airing date. Are you excited to swim with your favorite character again Free! fans!. We just have to wait until summer and we can see our dear swimmers again! What do you think will happen? comment below.
Featured photo and information taken from http://www.otakutale.com/2017/free-anime-season-3-announced-for-summer-2018/