藻掻く[mogaku] to struggle
海藻[kaisou] seaweed
褐藻[kassou] brown algae
珪藻[keisou] diatom
珪藻土[keisoudo] diatomaceous soil

紅藻[kousou] red algae
才藻[saisou] poetic talent
稚海藻[wakame] wakame (species of edible brown seaweed, Undaria pinnatifida)
藻草[mogusa] water-plants