A monocular will give you better optics for a given price, brighter optics for a given weight and most are waterproof (at least to the degree necessary for kayaking) since they don't have the openings necessary for a binocular's focussing mechanism. I have a 6X x 30mm, rubber armored Brunton monocular that's great for most purposes and provides a crisp, bright image. I also have a 10X x 30mm (?) Bushnell, but it's harder to hand hold and the optics aren't quite as good as Brunton's.

Whether you go "mono" or "bino" don't get carried away with power. A good 6-7x glass is all the magnification you need for most purposes and is about the practical limit for hand holding, particularly in a boat. Also keep in mind that there is an inverse relationship between size and brightness. Tiny optics are dark, no matter how good the glass. Stick with glasses that have an exit pupil (objective lens diameter divided by magnification) of at least 3mm, with 5 mm being optimum (my 6 x 30 Brunton has a 5 mm exit pupil, the 10 x 30 Bushnell's exit pupil is 3mm).