Claim: Octopuses have three hearts, and two of them stop beating when they swim

The claim that octopuses have three hearts, and two of them stop beating when they swim is mostly true. Research from marine biology sources confirms that octopuses possess three hearts: two branchial hearts for pumping blood to the gills and one systemic heart for the rest of the body. When swimming, the systemic heart does indeed stop beating, which is why octopuses prefer to crawl rather than swim. There are no significant disputes against this claim in the available evidence, reinforcing its validity. The models diverge sharply — treat this as higher-uncertainty. OpenAI comes in highest (90%), while Gemini is lowest (55%). OpenAI expresses higher confidence than Perplexity on this claim. While the evidence strongly supports the claim about octopuses having three hearts and the systemic heart stopping during swimming, there is a lack of opposing sources or significant debate on this topic. The absence of contradicting evidence suggests a consensus on the physiological characteristics of octopuses. However, the claim's nuances regarding the operational mechanics of the hearts during different activities could be further explored in more detailed biological studies.