Bell legibility at a distance. A jellyfish design earns its place when the bell shape reads as a jellyfish from across a room, not as a generic blob or mushroom silhouette. Symmetry, trailing tentacle lines, and visible oral arms help the recognition land cleanly.
Niche-vocabulary cues. The strongest jellyfish t-shirts speak the language the community uses with itself: 'jelly', 'just keep drifting', 'team jellyfish', 'I am a jellyfish'. That signals to other ocean lovers and aquarium fans, not to the general gift-shop audience.
Style-register clarity. A vintage 70s beach jellyfish illustration belongs to a different wearer than a dabbing kids' graphic or a minimalist verbal-quote design. The guide keeps designs whose style register is decided and consistent, not muddled across registers.
Wearer-identity fit. Jellyfish apparel splits across audiences: marine biology students, aquarium volunteers, jellyfish moms and dads, and kids who discovered the genus on a field trip. Each design here lines up with a clear wearer, not 'anyone who likes the ocean'.
Gift-readiness across ages. A jellyfish t-shirt that suits a six-year-old after a Monterey Bay visit is not the same as one that suits an adult aquarist on World Jellyfish Day. The picks here cover both ends so a gift buyer can match the recipient's age and context.