By car
Many of the hotels chains have a "water taxi" or a small minivan that will take you to the mall and main shopping areas. Taxis are very inexpensive, with most 10 minute rides costing about SR10-20 about $3-6. There are two types of taxis: one is yellow and will have a sign that says, simply, TAXI. They are usually cheaper, but a little "rougher" on the inside and out and and usually are not air conditioned. But they are very rare in Jeddah now. Also, most of them are now airconditioned new cars. If you're looking for better quality, opt for the white "Limousine" taxis which are of better quality. There is a rule in KSA that a Limousine must not be older than 5 years. So, you find all the new cars in Limousines. Limousine taxis are about $1-3 more expensive. There are also "unlicensed" taxis, those are normal cars usually a Toyota Camry without the "TAXI" sign. Those taxis are cheaper than "Limousine" but these Taxis are not legel. Police take strict actions against such Taxis. So try not to sit in such private Taxis. Normally they honk or flash lights when they see you standing in street you can't recognize them as they're normal cars.
Take note that you can negotiate taxi driver for a fixed price, which is much cheaper than using counter. This needs some "experience" with Jeddah and its streets. Sometimes taxi driver will pretend to be "lost" so he would turn on the counter or make you pay extra in exchange of his "lost time". whatever is the situation, never accept to pay more than you agreed on at the beginning of the ride.Also take note that some Saudi drivers ask for higher price and don't treat clients very well. Instead go for Indian or Pakistani drivers.
Many rental agencies like Avis or Budget will rent you a 2008 mid-size car for the price of SR100-140 about $30-50 per day. You'll also find a bargain when it comes to fuel, as Saudi Arabia has some of the cheapest petrol prices in the world. The streets are wide and signs are written in both Arabic and English. Look for maps in the libraries or big supermarkets.
By ship
Boats are not particularly a means of transportation, but rather a way to enjoy the views of the Red Sea. You can catch boats in Obhur north of Jeddah at the marina; a one hour ride in a small boat is around SR200 US$55.
By bus
Buses are not a commonly-used means of transportation in Jeddah even though you can ride one for SR1-2 from certain main streets to Albalad downtown. It is, however, a very interesting way to enjoy traditional Arab music and the sound of people mixing together all while enjoying sights during the ride. Smaller buses are mostly private so the owner is responsible for cleanliness. Larger buses are provided by the government, which are big and clean but don't follow a schedule, so consider using the smaller buses if you're on a specific timetable.