I had a player who wanted the same powers your player wants. He wanted to be a half sea-elf (with a stronger focus on sea elf to get the goodies, even though a half-elf does not get em). I layed the smack as follows:
1- He can have the water breathing and the +8 to swim skill that all aquatics get and be a +1 ECL.
2- Or he can have the water breathing but NOT the +8 to swim skill (no webbed feet, hands, but has gills) that all aquatic types get and have no ECL penalties.
He is still classified as an aqautic type, and thus can be affected by magical items that affect these creatures. I gave it a +1 to ECL as the campaign was based on islands and sailing. If my campaign was based on a non-water type overland, I would have let him have it with no +s to ECL.
1- He can have the water breathing and the +8 to swim skill that all aquatics get and be a +1 ECL.
2- Or he can have the water breathing but NOT the +8 to swim skill (no webbed feet, hands, but has gills) that all aquatic types get and have no ECL penalties.
He is still classified as an aqautic type, and thus can be affected by magical items that affect these creatures. I gave it a +1 to ECL as the campaign was based on islands and sailing. If my campaign was based on a non-water type overland, I would have let him have it with no +s to ECL.