I am currently designing a highly intelligent species for a sci-fi project I am working on. They are quite similar physically to prehistoric salamanders or similar amphibians, but I am having trouble coming up with a reason they would evolve arms longer than their legs and becoming hexapeds (so they can have the ability to construct tools in the future), because wielding tools with their forearms would be difficult on land, while still walking low on all fours
The only reason I have for them to evolve longer arms early in evolution (seeing as the bone structure is already available to grow these limbs) would be to walk or hold onto the sea floor. But those don't seem like necessary traits for a creature that can already swim and walk on the sea floor with relative ease.
Other than that I am stumped. Would there be any other reason a sea dwelling organism (or amphibians) would want or need the extra, longer limbs?