I only learnt to swim with Total Immersion 2 years ago. I have swum only in the pool up until now, but want to transfer to open water. I'm hoping to get some lessons. The Open Water Swim teacher recommended the Ocra S7, but my daughter who is a beach lifeguard, says they're a waste of money, and any 3mm core and 2mm legs wetsuit will do - is this true before I spend 229 euros? Would welcome any advice on buying a wetsuit for complete beginner.