The big fish have insulated themselves well. Howev

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Remoras have their front dorsal fins modified into large suckers with which they cling onto a host animal such as a whale, turtle, shark or ray. It is probably a commensal arrangement as the remora can move around on the host, removing ectoparasites and loose flakes of skin, while benefiting from the protection provided by the host, and the constant flow of water across its gills. Although it was initially believed that remoras fed off particulate matter from the host's meals, this has been shown a falsehood, in reality their diets are primarily composed of host feces instead .

https://en.wikipedia.org/wiki/Remora

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