I'll never swim with you again (from left to right and and top to bottom)
Sharks can't swim upside down. I think its called coma state. And I am pretty sute that killer whales do out to them. Drawing by Merman in my Teacup.
Seaworld AU by Fayolinn (Rin and Sousuke are trainers - for dolphins and orcas, respectively - and as they both end their day one day, they find that Haru and Makoto look a bit different. Now they have to keep the two mermen hidden.