Why do fish have vertical tail fins and whales have horizontal

What are the advantages and disadvantages of vertical tail fins in sharks versus horizontal tail fins in dolphins? - Quora

A tail with horizontal flukes hi-res stock photography and images - Alamy

How to tell the difference between a shark and dolphin by their fins

Where do Whales come from? A look at evolution.

science based - Is it more likely that merfolk would evolve with horizontal or vertical tails? - Worldbuilding Stack Exchange

Why orcas are more 'caring' than 'killer' whales - BBC Science Focus Magazine

Why do aquatic mammals like dolphins and whales have horizontally oriented tail fins while fish have vertically oriented ones? - Quora

Natural History Magazine

Why do some fish have vertical tails, and others have horizontal tails? - Quora

All Fish Have Vertical Tails While All Whales Have Horizontal Tails. Why?

Are Whale Sharks Whales or Sharks? (Here's The Truth) – Ocean Action Hub