i hope this answers your question.
Phytoplankton is the small plant life that whales and some other sea life eat. Many other forms of sea creatures eat fish and other sea creatures.
Large creatures live in the ocean, eat other animals, and get eaten by other animals. (example: Sea Turtles eat Jellyfish)
Some sea creatures have ansetors of dinosaurs
Some plants eat plankton and other small creatures.
If you mean, "are all under water creatures, sea creatures?" then no. The term SEA is for the ocean and there also can be creatures in freshwater. Also some creatures that live in water such as some snakes and sea turtles come out of the water every so often, so they are no total sea/water creatures. Fish are underwater creatures though.
Any sea creature, from the blue whale to the smallest krill, will be eaten by other creatures when they die.
sea stars mainly, and some other sea creatures that eat away at the coral reef
Yes every day by other deep sea creatures.
Some people believe in the existence of mythical or cryptid sea creatures like the kraken, mermaids, and sea serpents. These creatures have been part of folklore and legends, sparking curiosity and inspiring stories throughout history. However, there is no scientific evidence to support the existence of these creatures.
some
They feed on fish and other small sea creatures.
None, all sea creatures eat each other if no food .