This year's HTC Nexus's name has been leaked by Evleaks

Google's 3D touch nexus is on its way, and now, we know that there are two models, the HTC Google Nexus M1 (codenamed Marlin) and the HTC Google Nexus S1 (codenamed Sailfish). They are probably going to be different sizes, like last year's Nexus 5X and 6P, with their 5.2 and 5.7 inch screens. We presume that it's going to be the same this year as well.
We have no idea why the codenames of the phones are based on Finding Nemo, but it shows what the letters stand for.