First of all, many people don’t know about the dangers of wearing contact lenses in the water. Wearing contact lenses in any kind of water, whether it is an ocean, a pool or even a shower, is risky because bacteria in the water could cause an infection if they get under your lens. Unless you are wearing a mask or goggles that are 100% sealed and don’t let any water underneath, wearing contacts in the water is not recommended. If you do decide to wear contact lenses in the water, it is recommended to discard them immediately upon exiting the water.
You may have to adjust to viewing with a corrective dive mask because the lens might be further from your eyes than you are used to with your regular eyewear.
In general, pre-made prescription lenses on both goggles and masks are cheaper than the custom made options. In most cases, since you are using them for a relatively short period of time, the pre-made options can suffice. If however, you are a serious diver and want to see as clearly as possibly, it may be worthwhile to look into a custom made mask.