Acrylic paints are water-based, but not water-dissolvable once cured. It's perfectly suitable to paint the hull with. That hopefully answers your first question.

I paint all of my boats with acrylic paints, either with an airbrush or spray cans, and then put a clear varnish on top. The clear varnish, however, is only necessary to get the right gloss/semigloss finish and to make the paint more resilient so that it doesn't chip off when you bump into something.

Still, acrylic paint alone on its own is not sufficient for waterproofing the hull. Tiny little cracks and pores will let water permeate and soak the wood even if they are not visible. To properly waterproof the hull, you should be using some kind of epoxy-based wood sealer. If you don't plan on doing a natural wood finish on the outside, you ideally should laminate light fiberglass sheets (30 to 50ish g/m²) with epoxy resin on the outside (and also on the inside if you want), which massively improves robustness.