In a floating manner; while floating or in a way that suggests floating.
From floating (float + -ing, present participle) + -ly (adverb suffix from Old English -lice). This adverb describes the manner in which an action is performed, following standard English patterns for forming adverbs from adjectives.
The -ly adverb suffix is so common that English speakers add it to almost any adjective without thinking, creating words like 'floatingly' that may never appear in dictionaries but are instantly comprehensible to any native speaker.
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