Although the initial commitment may seem scary, computers are an important piece of diving equipment. They allow you to monitor your maximum dive time, allowing you to get the most from your diving. They are also a store for all your dive information, from depth to dive tme, and some can even record your air capacity which will make it easier to fill in your dive log book. Dive guides and budies will have different dive profiles so you cannot rely on these for your diving.
Computers are personal to you and follow you through all your dives. Although you can hire these, we recommend you to have your own.