Note: UA suggests that the Aquatic racial variants may deserve a LA +1 in some campaigns.
Originally Posted by SRD
Aquatic Race Level Adjustments
None of the aquatic races have level adjustments when your entire campaign is set underwater and all the PCs have the aquatic subtype, or when playing a nonaquatic campaign. The advantages gained by an aquatic character when in an aquatic environment even out with those of other aquatic characters, and their disadvantages in nonaquatic environments make up for any advantages they might enjoy.
However, when a mix of aquatic and nonaquatic characters occurs in an aquatic or ship-based campaign, aquatic characters enjoy a distinct advantage over their land-based cousins. In this case, consider applying a +1 level adjustment for all aquatic races, due to their swim speed, improved low-light vision or darkvision, and other special abilities.
* Expanded Psionics Handbook suggests alternate favored classes for the Duergar, Githyanki, and Githzerai (p. 6).
* Races of Faerun lists Forest Gnomes as LA +1. The version in the MM/SRD has exactly the same qualities, and is not listed with a level adjustment.
* Fey'ri are a unique case (AFAIK) as they get to chose 4 qualities from their list of available Demonic Abilities. Depending which four are selected, the race is either LA +2 or LA +3. Consult Races of Faerun.
* The Aquatic Elf in Stormwrack is erroneously (?) listed as a LA +1 on Table 2-1 (p. 34). In their Racial Traits entry (p. 40) the have no listed level adjustment. This is a case of text trumps table.
* The Crucian is listed in some sources as a playable LA +2 with no RHD. In both Miniatures Handbook and Sandstorm, it's monster entry lists it with 3 Humanoid RHD. The confusion probably comes from the "Crucian Characters" section in Sandstorm (p. 145) which omits racial hit dice as part of the description. For the sake of completeness, please see below for Crucian Racial stats, in case it is another case of text trumps table (although I don't believe this to be the case). Note: The reptilian subtype was present in MH, but not in Sa.
- Crucian - medium humanoid (reptilian ?) (Sa) +4 Str, -2 Dex, +6 Con, -2 Cha, Druid, LA +2
* I'm going to mention the Petal from MM3 here - their LA is listed as +2 (cohort), meaning they are only intended as NPCs, but many groups handwave this and allow them as playable race:
- Petal - tiny fey (MM3) 15 ft move, fly 60ft, -8 Str, +10 Dex, +4 Con, +4 Int, +8 Cha, Sleep Songs, DR 5/cold iron, (?), LA +2
So who are the "winner and losers" on the total ability mod front?
- LA +1: Blue, Dromite and Snow Goblin come in at a pathetic -2. WotC have some serious hate for Goblinoids.
Empty Vessel is the clear winner, with +10 (with bonus skills and a bonus feat to boot). Catfolk and Merfolk net a +6 to abilities.
- LA +2: The Gloaming and Volodni come in at +0, while the Ixitxachitl comes in at +10 (weighed up against no land movement, of course).