Mermaid Tattoo
As for the mermaid, well, we don't necessarily know why he got it, though he did tell Hollywood Life in 2014 that it's because he is a mermaid, but he did tell a fan that the mermaid has "saggy boobs" because "Everyone should love themselves for how they are. They shouldn't strive for perfection."
Rose Tattoo
The other big tat on his forearm is the rose. It's unclear exactly why he got it, but it's beautiful.