The bulk update request #9723 is pending approval.
create implication sea_turtle (174) -> marine (140147)
create implication sea_snake (90) -> marine (140147)
create implication marine_iguana (33) -> marine (140147)
create implication sea_otter (397) -> marine (140147)
create alias marine_reptile (7) -> marine (140147)
create alias marine_mammal (43) -> marine (140147)
Reason: Ichthyosaur and plesiosaur imply marine, but none of our living marine reptiles do!
https://en.wikipedia.org/wiki/Marine_reptile#Extant_groups
I think sea turtle and sea snake are pretty inarguable, and the marine iguana's lifestyle seems pretty similar to pinnipeds (which do imply marine) in terms of amount of time spent on land. However I have excluded the American and saltwater crocodiles, which I feel are marine reptiles in the same way the polar bear is a marine mammal.
(I've also thrown in the sea otter for marine: "Although it can walk on land, the sea otter is capable of living exclusively in the ocean.")
Marine reptile and marine mammal could be umbrella tags, but I think they're unneccessary, let me know if you disagree.