What's wrong with snark? You left out a possibility: 1. The islands were similarly submerged 23 years ago. [close to submerging, but sure] 2. The sea level d

What's wrong with snark? You left out a possibility: 1. The islands were similarly submerged 23 years ago. [close to submerging, but sure] 2. The sea level data is somehow inaccurate. [always must be included] 3. Sea levels are at the same point, but geological factors may be causing the islands to sink. 4. The sea levels are generally higher, but are currently in a lower point in their regular cycle - similar to what happened in 1998. Now, I won't make any claim either way about this without doing more research. But it should be abundantly clear that the value oscillates (with several effects that have different periods) and therefore you must include those in your list of possible explanations. And also that the instantaneous value, taken in a vacuum (ignoring all predictions we can make from the periodic effects), is utterly useless for predicting what will happen in the next 1-50 years.