Every dive bag argument ends the same way at a check-in counter. The flight to Port Blair gives you fifteen kilos, and a full set of personal kit is most of that before you have packed a shirt.
Bring: your mask
Two hundred grams, and it is the single piece of equipment where fit is personal and rental is a lottery. A mask that leaks turns a good dive into forty minutes of admin.
Bring: your computer
Not because rental units are bad, but because your own logs your dives, you know its beeps, and you are not learning a new menu at 24 m. If you own one, it comes.
Bring: a 3 mm shorty, if you own one
Optional in 29-degree water, but a rented full suit in the wrong size is more irritating than being slightly cool.
Leave: BCD, regulator, fins, tanks
Nine kilos of your allowance for equipment that is included in every price on this site and serviced quarterly. Unless you are diving forty times a year, it is not worth the flight.
Bring anyway
Reef-safe sunscreen, a steel water bottle - the marine park will not let you land with plastic - twice the memory cards you think you need, and a paper copy of your certification. Phones die.