Both are BL series where one of the characters has a girlfriend and struggles with coming out. They also go beyond the norm in showing affection, even though Water Boyy has only *spoiiler* one real kiss. Also, they have other characters with a story of their own. Plern Pleng and Waii's girlfriend act similar (but Pleng is actually a villain). Both deal with BL in a more mature way than usual too.
They both are Swim team Dramas, however the ''movie'' was a older version lets call it the original, and ''water boyy'' is a updated version, Now my opinion is that the characters were great and the chemistry was well scripted and the actors did a great job of conveying there character as if they were real people . A much more comedic feel that you can get that feel good factor while just engaging in the plot and letting it all sink in.