These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Les Yay: Quite subtle aside from Jenny and Lynn. Marika/Chiaki. Marika/Gruiernote Gruier once bought Marika a suit. Marika usually wears a short skirt. Marika thought the miniskirt on the suit was too short. Gruier argued vehemently that it was perfectly fine. Marika/Mami. No wonder some fans joke about Marika's "harem".
Series Continuity Error: At the beginning of episode 16 there's a wide external shot of the hospital station, which shows the Bentenmaru docked with it, even though the Yacht Club is actually out sailing in it, preparing to make a pirate raid.
Shipping: The anime has gotten some attention from the yuri fandom thanks to its large amount of female cast and the fact that Word of God stated that there is no romance. Yuri fans presumed that he meant "there is no male/female romance", especially after Jenny and Lynn started exploring each other's tonsils onscreen. And with that said, Marika gets shipped with a lot of girls, specifically Chiaki, Gruier, Grunhilde, and Mami. Interestingly enough, Marika and all those girls are seen together in one part of the ED sequence.
Shipper on Deck: Chiaki's dad, of all the people, is implied to ship his own daughter with Marika.