Every meguca is canonically thalassophobic. I mean, every normal person already knows this because normal girls don't go swimming. The authors didn't even thought about the possibility of western ocean-loving shizos interpreting the chacarcters that way. There is no ocean in the anime in the first place. Only in gachaslop pandering to the mentally ill swimtards do megucas go to a beach. Ocean is consistently depicted as a horror through the imagery of Uhrmann, Octavia, and Walpurgisnacht flooding the destroyed city. Sayaka's arc shows the dangers of succumbing to the degeneracy of swimming by drowning in her labyrinth. In the 12th episode Madoka commits Total Oceanigger Death which is why Rebellion takes place in the desert.