[eesmith]

Some dolphins use tools.

"In Shark Bay, Western Australia, bottlenose dolphins Tursiops sp. carry conical sponges Echinodictyum mesenterinum on their rostra in the only documented cetacean foraging behaviour using a tool" - https://www.int-res.com/abstracts/meps/v444/p143-153/

Also, octopuses: "The use of tools has become a benchmark for cognitive sophistication. Originally regarded as a defining feature of our species, tool-use behaviours have subsequently been revealed in other primates and a growing spectrum of mammals and birds [1]. Among invertebrates, however, the acquisition of items that are deployed later has not previously been reported. We repeatedly observed soft-sediment dwelling octopuses carrying around coconut shell halves, assembling them as a shelter only when needed." - https://www.sciencedirect.com/science/article/pii/S096098220...

Lastly, your terrestrial experience might limit your understanding of what a 'tool' might be: "tool users in water often use other animals (and their products) and water itself as a tool ... Octopodes, as well as squids and cuttlefishes, also use water as a tool for protection by using jets of water to aid in burrowing for camouflage ... Humpback whales (Megaptera novaeangliae) singly and collectively expel bubbles to create nets that encircle, contain and concentrate schooling prey for easy gulping " - https://royalsocietypublishing.org/doi/full/10.1098/rstb.201...