I do videos for on my Hobie 16 when I'm at regattas and for fun. I'm usually camping so at night I have my GoPros charging in my tent. Even with using the anti fog tabs my videos always fogged up. The can look completely dry, but when the electronics of the GoPro warm up any bit of humidity goes right to the lense. The trick I learned is to always store my gear in a dry box with a mini dehumidifier. This was a complete game changer and I intend to modify my dry box so I can pass power into it for charging while all components that are used on the water are kept as dry as possible. The only place I store my GoPro gear is in my dry box now.
The dehumidifier I use: https://www.amazon.com/dp/B000H0XFCS/
The dry box I use (thinking about getting a bigger one though): https://www.amazon.com/dp/B001A1VE8A/
Video from July before I used the dry box and dehumidifier (you can see fog rings at various times): https://youtu.be/3QQDN2frMT0
Video from November after leaving my equipment in the dry box for a few week (zero fogging even with 55 degree air temps): https://youtu.be/sSXyEzIKU4c
Laptop to free up space on the SD cards is a great call, but I would recommend having additional SD cards so you don't have to wait 20 to 30 minutes for a full SD card to download to your laptop if you want to make a quick swap.
For being out on the water I would never trust the jaws or suction cup. For doing video on big boats I use this: https://www.amazon.com/dp/B0062U2M4E/ with some adapters to get it to GoPro mounting system. There are also GoPro handel bar mounts that I would put around various poles on the boat.
For on my H16 I use these adapters that I have permanently riveted to a couple places on my boat. https://www.amazon.com/dp/B005YVTK42/
No matter what kind of attachment I use I also do a safety line with some high strength kite string.
Oh, and the expanded batter packs are a must. They can fill up most of a 64gb card on one charge.
And don't skimp on the quality of your SD cards. GoPros write a lot of data quickly and the cheep ones can't keep up and will ruin your video...or just give up trying.