This might be a strange question, but why do sea turtles lay eggs on land and not for example dig up holes inside the ocean? They live their whole lives in the ocean, so why do they lay eggs on land? Why travel so far just to lay eggs?
Same goes for some salmon, why do they leave the oceans and lakes, and go upstream on rivers and not lay their eggs where they live?
It is probably something to do with protecting their offspring, but it seems to me that they still have predators that hunt their offspring fairly easily where they hatch/lay their eggs, so maybe there is another reason as well?
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Good answers so far but there could be one additional reason: By sheer happenstance, the hatching of turtle eggs on a beach creates a kind of selection pressure that wouldn’t otherwise be created in a “safer” environment(Let’s assume that there were no environmental problems like temperature and O2 for laying eggs under the ocean floor, which are the main answers to this question).
So in simpler words: Making your hatchlings run a predator filled obstacle course offers more selection pressure, which leads to more robust turtles
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