Hoping for a bit of honest advice.

Is it at all possible/advisable - to get started in boating on the south coast dorset/sussex (maybe some parts of kent) - WITHOUT any training. Is it safe in a smaller boat, staying very near.....or is there really a necessary minimum level of rya training etc.

Alternately, same question for river boating (e.g. thames around berkshire etc) - is that more accessible and do any of the skills crossover much?