A Grape! ....no its a type of Algae called 'Lavender Crust'
Rhodophyta , which just means its a red algae.
Blue green algae on ambergris just recently caught my attention . I really wasn't giving it much thought when evolutionists said we sprang from Blue Green Algae but Its skeletal remains wash up after a storm and are calcium. Never thought of a plant having a skeleton.