So I finally bought a paddle board. It's a second-hand 12'6 x 28.5 old-school NSP job in sound condition. It's my first board and I went for my first paddle today in flat conditions.

I'm 185cm and weigh 105kg but am getting back to my standard weight of 95-100kg fairly quickly.
The board is really tippy, I can stay up for about 5 minutes but then succumb to gravity.
Does it take a while to get your paddle board legs or should I have bought a bigger board? I really wanted a 14 footer but my I'm a bit tight on cash at the moment and only had $500 spare, which is what my board cost.