A dive boat is a boat that recreational divers or professional scuba divers use to reach a dive site which they could not conveniently reach by swimming from the shore. Dive boats may be propelled by wind or muscle power, but are usually powered by internal combustion engines. Some features, like convenient access from the water, are common to all dive boats, while others depend on the specific application or region where they are used. The vessel may be extensively modified to make it fit for purpose, or may be used without much adaptation if it is already usable.

Dive boats may simply transport divers and their equipment to and from the dive site for a single dive, or may provide longer term support and shelter for day trips or periods of several consecutive days. Deployment of divers may be while moored, at anchor, or under way, (also known as live-boating or live-boat diving). There are a range of specialised procedures for boat diving, which include water entry and exit, avoiding injury by the dive boat, and keeping the dive boat crew aware of the location of the divers in the water.

There are also procedures used by the boat crew, to avoid injuring the divers in the water, keeping track of where they are during a dive, recalling the divers in an emergency, and ensuring that none are left behind.

The dive boat provides a means of transport to and from dive sites which may be too far or inconvenient for shore access. This is the case with the majority of recreational dive sites. It can also provide a base of operations where the divers can shelter, rest, store and change gear, socialise with other divers, eat and sleep between dives. They can provide enhanced safety, comfort and convenience, and provide guided access to sites of particular interest, but introduce their own set of hazards. They can also provide access to diving procedures which may be difficult, dangerous or impossible from the shore.

The usual classification of recreational dive boats based on operational parameters includes:

Some overlap of function is possible. Dive boats may be privately owned and operated, or run as a commercial business (generally known as charter boats).

The structure, layout and size of a dive boat for any given application may vary considerably according to regional requirements and traditions, and convenience.

These are usually open boats used for short distance, or short duration, trips to dive sites, usually for a single dive or sometimes for a "two tank" trip, either with both dives at the same site, or with the second dive on the way back, or a short distance from the first. They generally have no amenities other than seating and stowage for dive gear, and the divers are usually exposed to wind, spray and sun during the trip. It is common for divers to kit up in their dive suits before boarding, for protection from the weather. It is unusual for the operator to provide refreshments other than bottled drinking water and an after-dive candy.^{[citation needed]}