Southwick is broadly safe by local-authority standards. About 66 recorded incidents per thousand residents over the last twelve months. Roughly 5% below the Adur average. Around 917 incidents on the town's own count for the same window. The town does not headline anyone's list of dangerous coasts, and it does not clear anyone's list of gentle ones either.
The published crime rate for the town runs at about 66 recorded incidents per thousand residents over the twelve months to March. That sits roughly 5% below the Adur figure of about 69 per thousand across the local authority as a whole. The absolute count comes out at roughly 917 incidents across the same window. That is the type of number that reads either as reassuring or alarming depending on what you compare it with, which is exactly why the local-authority comparison is the useful frame. Southwick sits at or slightly below the average for its regional peers, rather than above them. That does not mean nothing happens. It means the total, per head, sits in the ordinary band. Two things the town-level rate does not tell you: which categories of incident drive the total, and which specific streets carry more of the load than others. Both vary enough within a town this size that any street-level statement on a page like this would be inventing detail the numbers do not carry. The police mapping tool at the postcode level is where those specifics live. Anyone with a specific address in mind should treat that map as the actual answer, rather than the summary rate a town page can offer.
Three out of five is the honest verdict on safety. Not the sort of place where safety is the reason you would not move there, and not the sort of place where safety is the reason you would. An average coastal-town read on the crime rate, which is roughly what a small town on the West Sussex coast tends to produce, and roughly what most long-term residents would tell you if you asked. Fine for most streets, worth a closer address-level look for anyone whose particular street matters more than the town average. The verdict any purchaser needs is not on the town. It is on the postcode.