Life started everywhereUncommonDescent features a newly discovered walking shark. Surprisingly, walking sharks are fairly common.
The video is done by Attenborough, high priest of Gaian genocide, but he manages to get through two minutes without mentioning Gaia. The shark itself is amazing. If it hadn't been identified as a shark, I'd be sure it was a salamander.
Note the gait pattern. It's the same as familiar mammals. Front feet move opposite to back feet.
Swimming fins don't move this way; both fronts move together, and both backs (when present) move together. Turtles have both gaits available, and use them appropriately.
In other words, the gene for walking is present in all animals, and it not only forms legs, it forms a gait pattern in the brain. The gait pattern comes with a decision mechanism.
The old story that life started in water and moved onto land just doesn't work. Life started everywhere, so life started with the genes needed to live everywhere.