Theseus arrives at Poseidon's sea palace:
Theseus (bows): Good afternoon, Queen.
Amphitrite (scrutinises him): Wait… you have something on your head.
Theseus (touches his hair): Do I have any algae?
Amphitrite: Posidonia isn't algae, it's a plant.
Theseus (blushing bright red): I'm sorry, Queen… I just wanted to make a good impression.
Amphitrite: Oh no… what a nice boy, Poseidon. May he stay for dinner.
Attic red figure terracotta kylix, attributed to Briseis Painter, ca. 480 BC. Metropolitan Museum, USA.
Well she is crowing him but we could also hc that Amphitrite is one of those people who gets annoyed when they see things out of place, such as a hair on a jumper or a leave in the hair.
The scene seems to belong to fragment 17 of Bacchylides
where Minos, to prove whether Theseus is truly the son of Poseidon, throws a jewel (traditionally a ring) into the sea and Theseus jumps into the water and arrives with dolphins at Poseidon's palace, where he is received by Amphitrite, who dresses him in a purple cloak and presents him with her own wedding crown, made of roses by Aphrodite. AAAAAAAGHHHH🌹🌹🌹🌹
A little take to Posidonia oceanica:
As Amphitrite has emphasised, it is not a seaweed but a plant, specifically an angiosperm, also known as a marine phanerogam, and this particular species is the most important in the Mediterranean. It forms extensive meadows, capable of hosting a high biodiversity of species. The meadows provide shelter, food and a nursery for juveniles for many species, produce oxygen daily, while capturing carbon dioxide from the atmosphere and creating tonnes of biomass per year.
(up and donw, left to right): Posidonia meadows; leaves and a flower; flower; fruits floating in the sea; germinated fruit
And yes, it is named Posidonia after Poseidon. Isn't everything absolutely wonderful?