In UK you could sue a seller (only if he is acting in the course of business, so private sales do not fall into that category) under the Contract of Sales Act terms, which can not be waivered out. To summarize without too much details, the law stipulates the goods need to be appropriate for the use they are intended for and also that they are appropriate for the particular use a buyer is intending to use it for, having informed implicitly or explicitly the seller about the use it is going to be put up to.
In the UK and the whole EU you could also sue a manufacturer under the Product Liability Directive if you can prove that the product was defective by being less safe than the public is generally entitled to expect. You do not need to prove anyone’s fault why the product is defective, only that it is defective within the definition of defectiveness.
in this scenario, if it happened in UK, if the seller was made aware that the dry suit is for an inexperienced diver who never dove it and only had few dives experience in total, it could be argued that the good was not fit for the intended purpose communicated to the seller. If the seller was not aware who is it for and was only asked for a drysuit for cold water diving, there would be no cause of action.
in terms of manufacturer’s liability, you would have to prove that this particular brand/model is more prone to accidents than other comparable drysuits and hope that statistical evidence convinces the judge. Alternatively, you can prove that there was a manufacturing defect of some sort or a design defect in this particular model which made it ‘less safe than general public is entitled to expect’.
Because some goods are inherently dangerous, like a gun or a rebreather, it doesn’t make them ‘defective’ just because they are dangerous to handle and can injure or kill you at a rate higher than other goods put up to use - the Directive allows for these type of goods.