Describe a food web that includes a blue whale, krill, tuna and a shark. Add other organisms to make it work.

The KRILL eat ALGAE. PENGUINS, TUNA, and BLUE WHALES eat the KRILL. The PENGUIN is killed by a LEOPARD SEAL. SHARKS and KILLER WHALES eat the BLUE WHALES and the LEOPARD SEALS. So the algae goes to the krill. The krill goes to the penguins, tuna, and whales. The penguins go to the leopard seals. The whales and the leopard seals go to the sharks and killer whales making them top of the food web.

That would be a working theory.