What's exactly the problem with using for example Paddling for recording youe sea kayaking activities? Do you need to monitor different metrics than what that Activity type does? If so, then just define you own custom Activity type, name it Sea Kayaking, and set up the metrics in the way you need. Alterntively, if your device supports the Connect IQ technology, you can install one of several IQ apps for kayaking: https://apps.garmin.com/en-US/search?q=kayak
I'd mention that sea-kayaking would like to rather lock the barometer/altimeter to barometer-mode. Today recording of sea-kayaking would give me like 14m ascend on a 6km (3km one direction) trip. On a surface that is the definition of sea-level (not much tide at that time and place).