DART cannot communicate while in the water. Although, in reality, it's a team, and not one person.
DART does use pagers and cell phones. They are issued Motorolas and operate on the County TRS. They have access to most of the talkgroups. They've been on our channel, Fire, and I think even the SO and PD. They're an interesting group of volunteers, but people have mixed reviews of their performance. BTW-I have yet to see a rescue. Every time I've been out with them it's been a recovery.