You want a camera that survives a drop and a dive. A high-capacity waterproof model is meant to last years, not one season. We buy the good stuff once so we don't have to buy the cheap stuff twice. This usually means spending around $450 for something reliable.
Early spring is the time to look. New models usually drop in the fall, so by March or April, last year's flagship is often discounted. That older model is usually 95% as good for a lot less cash. It's the sweet spot for getting pro-level stabilization without the launch-day price tag.
This 0% interest offer is a deadline, not a gift. If you still have a balance on the card after the 18 months are up, the standard variable APR will kick in on whatever is left, making your camera much more expensive.