TUSA Caster Bag
GO-Dive price  £79.99

This sleek and competitively-priced model from TUSA is one of the best-designed models on the market today.
The CB2 is very much of the one-bag-for-all-uses school: there's enough capacity for a full set of kit, a good selection of clothes and a washbag (traveller's tip - always stow toiletries in an outer compartment in case your shampoo/shaving foam decides to leak). It may not have a solid shell, but the cumulative padding of the bag is such that it can survive some severe pummelling, and you don't have the extra weight that comes with a hard pack.