What are tankies? What does sea-lioning mean? - Lemmy.World

I’ve run across these terms several times, but without enough context to figure out what they mean. Could someone help me out, please? ETA All of you are amazing! A huge thank you to everyone who responded, and an extra thank you to those who have provided links or explanations to further and/or related information. I am learning so much by reading all of these comments!