Both series have young characters being awkward about sex and romantic life, almost the same type of comedy and tone, a cute romance that develops similarly. Although My Tee is better in every sense.
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.