Beach implies seaside, while beaches occur at lakes too. Take this picture for example: http://e621.net/post/show/268818
No sea, no seaside. It has a beach and a lake.

Additionally, I would like to suggest the following implications:
Lake --> water and gills --> marine. Gills suggest marine features, and therefor should imply marine. At worst a not water based hybrid character could have gills, but that would still qualify it for marine. Lake to water, no explanation necessary, as long as lava_lake doesn't imply lake.

Marine refers to something that lives in the ocean; you can have gills and not be a sea-dwelling creature.

Kclub said:
Marine refers to something that lives in the ocean; you can have gills and not be a sea-dwelling creature.

The problem is that the species tag isn't "aquatic", as it should be to properly encompass freshwater species, but "marine" which would exclude freshwater anthros.

GreyMaria said:
The problem is that the species tag isn't "aquatic", as it should be to properly encompass freshwater species, but "marine" which would exclude freshwater anthros.

Separately, I would note that just because a species has gills doesn't mean it is definitely aquatic: e.g. land-based crabs.

I vote for making marine a subcategory of aquatic, the latter should be for water-based species and the former for purely oceanic species.

• marine +> aquatic
• shark, dolphin +/> marine

I also got a little carried away mapping species implications/aliases...

• sea_star => starfish
• sea_dragon => sea_serpent

• stingray, seahorse, catfish, goldfish, angler_fish, eel +> fish
• nautilus, cuttlefish, squid, octopus +> cephalopod
• sea_anemone +> anemone
• sea_otter +> otter
• sea_serpent +> sea_monster

• fish, jellyfish, anemone, shrimp, lobster, cetacean, seal, otter +> aquatic
• coral, sea_anemone, starfish, seahorse, cephalopod, orca, sperm_whale, narwhal, sea_otter, sea_lion, sea_monster, mermaid +> marine

Somebody else can do the pokemon.

(=> : aliases to, +> : implies, +/> : unimplies)