I agree with much of the above, strap everything down, carry a spare paddle, get used to how the kayak handles before you spearfish from it, in wind and any real tide if your using the kayak as a float, it will be pulling you, set up a decent anchor system, really easy to do and use a folding anchor designed for the job, they are really effective. The most important thing is to do you your research regarding local conditions, check weather forecasts, know the tide time, height and direction of travel. Also a VHF isn't a bad idea if your going any distance and tell some one where your going and what time you expect to be back. Kayaking is great, just remember that if your paddling distance, then diving and paddling back, keep something in the tank and have food and liquid on board. One final thing, always check the pressure plug in your kayak before paddling off, every sit on kayak has one, if you leave it open, your taking on water! Have fun and dive safe☺