Love this collecting idea! I have always been a Vileplume fan, and I definitely think it’s an underrated Pokemon.
Aquapolis Vileplume is a great card and comes to mind. Also Bilingual Exeggutor non-glossy from the TMB could be a grail card, it is such a charming Japanese card! Fortunately it also has a cheaper glossy version from Trainer Mag 3 that’s much more attainable.
In terms of cards with a reef feel, I think of Vending Krabby and Horsea that are Japanese exclusive and have amazing Kizuki art. The Venonat, Kingler, Seadra, and Staryu from the Vending series also have a great feel.
Others have mentioned the Southern Islands set which are a no-brainer to add In terms of other promos, the Information Pack Bellossom comes to mind aswell, and is also Japanese exclusive.
Look forward to seeing your progress and your collection grow
I just heard team of 6, and immediately thought of the video game and if that is the concept really appreciate that idea. You mentioned water pokemon which would be a must for surf and you would need a flying pokemon! I’m assuming one of the grass type would be able to learn cut so you got that already done!
The flying type that comes to mind is Pidgeot (just always remember grabbing a pidgey early on the 1st gen gameboy games)
The water type I always thought Seadra was really cool, and could work with your theme
I have decided on my Gen 1 Team that I am going to collect!
Vileplume and Exeggutor will represent the Rainforest and Coastal Flora
Tentacruel and Seadra will represent the local ocean and reef inhabitants, including the very deadly box jellyfish that are endemic to the region!
Venomoth is here to represent the massive insects that are endemic to the rainforests of Northern Australia!
Rounding it out we have Nidoking! The big man is here representing not only my favourite pokemon but all the terrestrial mammals and reptiles of the far north.
And lastly, though not part of the Gen 1 team and my all time 2nd favourite pokemon , is Feraligatr. Perfectly representative of not only my favourite animal but one of the most iconic and powerful to have inhabited Northern Australia, the Estaurine Crocodile.