I use a tripod on many occasions for wrecks, reefs and any shots where more than a 1/8th of a second is requird.
Just go and buy a nice cheap regular tripod, a second hand one is a good idea.
Make sure it is sturdy enough for your camera set-up and you can use all your camera functions in both portrait and landscape positions. Then go for 'it'.
Just make sure you give it a good soak in fresh water when you have finished and lubricate all moving parts before packing it away.
I have done this for years and have only wrecked one tripod because I didn't give it any lubrication after use. Salt water is after very hard on steel and aluminium.
Hope this helps.