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If you’re happy to pay for and use hire dive gear, I know pro uw photographers who only take the clothes on their back (often several layers) and a spare set of clothes. Then they take their camera gear with just maybe two ports and lenses. The other thing you can do is buy a jacket with massive pockets and get extra unweighed allowance that way. (Though in some destinations like Solomon Islands, they will weigh you and your baggage. Your gear can even be loaded onto the plane and then unloaded again and you can be bumped to different flights for days if the total weighed exceeds what the plane is capable of carrying).