I know that they are the writers of Nagi no Asukara, just that I wanted to know more about that exactly. A group being named after a "project" sounded curious to me. Can someone tell me more about these authors? (or author)
The meaning of "Project-118" is the sum of the name of the staffs in the planning stage converted to numbers.
It was explained in the "Nagi no Asukara" Special Staff Talk Show (凪のあすから 汐鹿生大宴会 ―「凪のあすから」スペシャルスタッフトークショー) on April 19, 2014. Some tweets from it:
The meaning of Project118. Tsuji (ed. the Animation Producer) said that if the name of the staffs in the planning stage of Nagi no Asukara is converted to numbers and then summed, the total is 118. Searching about it, it is the number of Japan Coast Guard. [...]
The meaning of 118 in Project-118 is, when the name of the staffs at the beginning of production decision is "matched"(?), the sum is 118. [...] ... By the way, looks like 118 is the number of Japan Coast Guard something, having "sea" as a common point is a coincidence.
(emphasis mine, archived from togetter (Japanese))
However, they didn't explain further about the conversion and who the staffs are.
It might be possible as nhahtdh's comment to calculate the kanji strokes of the name (example: 辻充仁 is 5 + 6+4=15), but it's also possible to use goroawase (example: 辻充仁, Mitsuhito Tsuji is 3+2+1+10 + 2+10 = 28 [or any other possible combinations]). But at this point, both are only speculation though.