I'm looking at getting an action camera for our upcoming cruise but don't know if I want to drop the cash on a GoPro because it won't be used very often. Can anyone sell me on getting the GoPro versus a cheaper knockoff? If not GoPro, can someone recommend a good knockoff. I'd like to shoot in 4k, 60fps if possible, and I'll be using it underwater.

I use a Garmin in conjunction with my airplane habit and think it works great. It of course can integrate with many of their other products from all sorts of categories, so if you already have some Garmin gear I'd recommend taking a look there.

I have no experience with GoPro or other products.

Hard to beat GoPro Hero 5 Blacks at the price they're going for now imo. Academy had them for $200 a few days ago. Here are some deals at Target and Best Buy, GoPro Hero 5 Black + $35 gift card for $250

If you're looking for a knockoff, check out the Xiaomi Yi 4K.